INTRODUCTION
While we were investigating gray whales ( Eschrichtius robustus ) caught during the winter of 1966-67 at the shore station of the Del Monte Fishing Company, Rich- mond, California, under a special scientific permit issued to the Marine Mammal Biological Laboratory of the U. S. Bureau of Commercial Fisheries, we made some observations on the baleen plates and parasitic barnacles. These results are re¬ ported here.
THE ASYMMETRY OF WEAR OF BALEEN PLATES
Measure- Fig. 1 shows the length of the baleen plates of two gray whales. ments were made on every 5th or 10th plate, from the gum line to the tip of the posterior view. Black line indicates the gum line. * Ocean Research Institute, University of Tokyo. ** Marine Mammal Biological Laboratory, Bureau of Commercial Fisheries. Sci. Rep. Whales Res. Inst., No. 22, 1970, 39-43. plate along the lateral edge. As seen in this figure, the length of the baleen plates in the anterior part of the series is not bilaterally symmetrical. The plates on the right side are shorter than those in the corresponding positions on the left side. This asymmetry appears to be the rule among the California gray whales, for among 31 whales observed by us, there were only 3 animals in which the baleen plates of the anterior part of the right side were longer or nearly equal with those of the left. As seen in Fig. 2 the distance between growth marks on the surface of the baleen plates is the same on the left and right sides, but the plates on the right side show heavier wear on the lingual edge. So it is reasonable to conclude that this asymmetry has been caused not by the slower growth of the right plates but by heavier wear on the right. The gray whale feeds on benthic organisms and sometimes even swallows sand or pebbles (Tomilin, 1954;  Pike, 1962;  Rice and Wolman, in press). Scam- mon (1874) and Wilke and Fiscus (1961) reported that feeding gray whales had surfaced with head and lips besmeared with mud, and that they apparently had expelled mud through the baleen. These observations suggest that gray whales scoop the mud or sand on the bottom to collect benthic organisms. Gunther (1949) mentioned that the movements of the rorquals from side to side appears to be restricted by the structure of body and that fin whales have the Sci. Rep. Whales Res. Inst.,
No. 22, 1970.
TABLE 1. MEASUREMENTS OF BALEEN PLATES OF CALIFORNIAN GRAY WHALE
C: At 50 cm from anterior-most bristle. tendency to swim on one side to turn sharply to one direction. The same would be true also for gray whales feeding at the bottom, and it would be difficult for them to scoop the bottom with the anterior part of the lower lip while swimming This is supported by the observation that the number of colonies in normal posture. of barnacles infesting the left side of the head region exceeds that of the right side. On the skin of the right side of the rostrum we often observed many healed or open wounds, probably scratches caused by hard substances on the bottom. From these considerations we speculate that the asymmetric wear of the baleen plates of the gray whale is the result of feeding movements in which the whales scoop the sediment mostly with the right anterior region of the baleen plate rows. No asymmetry was found in the number of baleen plates (Table 1). Sci. Rep. Whales Res. Inst., No. 22, 1970. WATER CURRENT ON THE BODY SURFACE SUGGESTED BY THE ORIENTATION OF THE BARNACLES There are many colonies of barnacles, Cryptolepas rhachianecti DALL, on the skin of gray whales. They are especially numerous on the rostrum and flippers, fairly numerous on the upper edge of the lower lip, the area between the eye and the base of the flipper, and on the tail peduncle. There are few barnacles on the other parts of the body. These barnacles are directed approximately towards the anterior end of the whale, and all the barnacles in a colony are oriented in the same direction. The orientation of barnacles at any point on the body is nearly the same in all whales. We think that the orientation of the barancles is affected by the direction of the water current at the point where the barnacles are growing, and the anterior end of the barnacles coincides with the mean direction of the current. Fig. 4 is a diagrammatic figure of the orientation of the barnacles on the gray whale. This figure is based on sketches of each part of the body of six animals, and some photographs taken in the same whaling season. Each small rod represents approximately one colony. We found no significant bilateral asymmetry in the orientation. On the upper jaw and the dorsal side of the tail peduncle the water seems to flow obliquely upward. But in the area between the angle of the gape and the anterior insertion of the flipper, the water seems to flow obliquely downward from the gape to the flipper. These flow patterns agree with those on the body of Del- phinus and Phocoenoides, as determined from the arrangement of dermal ridges and from a photograph of a swimming Delphinus (Purves, 1963). Purves (loc. cit.) Sci. Rep. Whales Res. Inst., No. 22, 1970. reported that the dermal ridges on the flippers and flukes are arranged perpendicular to the leading edge. But in the case of the gray whale the barnacles are oriented obliquely from the anteroproximal to the posterodistal edge of the fins on both dorsal and ventral sides. Probably the gray whale usually holds its flippers in a ventroposterior position, so the mean direction of the current will be oblique to the long axis of the flipper. On the tail flukes it is not unreasonable to think that the current moves in a posterodistal direction, when the flexibility and somewhat posteriorly convex shape of the flukes are considered. On the ventral side of the body the water seems to flow parallel with the body axis. The orientation of some colonies of barnacles suggests a downward flow slightly below the mid-line of the tail peduncle. Greatest thanks are due to Mr. Allen A. Wolman of the Marine Mammal Biological Laboratory, who kindly assisted at the whaling station.  Without his help, our study would not have been accomplished. We owe very much to Prof. Masaharu Nishiwaki of the Ocean Research Institute, who provided the opportunity for Kasuya to study the gray whale in the United States. The cooperation of Mr. John Caito and Mr. Charles Caito of the Del Monte Fishing Company is also acknowledged. They provided the facilities to collect and study the gray whales. Gunther, E. R., 1949. The habits of fin whales. Discovery Rep., 25: 113-42. Pike, G. C., 1962.  Migration and feeding of the gray whale (Eschrichtius gibbosus). J. Fish. Res. Bd. Can., 19 (5): 815-38. Purves, P. E., 1963. Locomotion in whales. Nature, 197 (4865): 334-7. Rice, D. W., and A. M. Wolman, (In press). The gray whale : life history and ecology. Amer. Soe. Mam- mal., Spec. Publ. No. 3. S CAMMON , C. M., 1874.  The marine mammals of the northwestern coast of  North America.  John H. Carmany & Co., San Francisco. 319 pp. Tomilin, A. G., 1954. Adaptive types in the order Cetacea. Zool. Zh. 33 (3) : 677-92 (cited in Pike, G. C., 1962). Wilke, F., and C. H. Fiscus, 1961. Gray whale observations. J. Mammal. 42 (1): 108-9. THE INSTITUTE OF CETACEAN RESEARC