DIE INNERE SEKRETION BEI WIRBELLOSEN TIEREN
Authors: (Kiel). G. KOLLER 
Published: January 2008

1. The presence of active sexual hormones can be assumed with a reasonable degree of certainty in cases where parasitic or experimental castration brings about specific changes in secondary sexual characters. One of the principal instances of this is the parasitic castration of decapod Crustacea (Carcinus, Inachus, Pagurus) by Rhizocephala (Giard, Smith, Potts, Nilsson‐Cantell, van Oordt), the result of which is, in male crabs at least, a definite approach to the female facies. It seems possible that the seat of formation of the hormones is not in immediate connection with the gonads themselves (Courrier). Similarly “stylopisation ”in the hymenop‐teran Andrena causes alterations in colour of the clypeus, differentiation of the tibia, etc., in both sexes, resulting in an unmistakable approach to the opposite sex (Pérez, Wheeler, etc.). Earthworms (Lumbricus herculeus), in which the testes are destroyed by parasites, lack the clitellum, a secondary sexual organ. This natural phenomenon has been confirmed experimentally by Harms.

The results of experimental castration indicate, as far as the present state of our knowledge goes, that there is a fundamental difference between Crustacea and insects. It has been definitely proved by the castration of Asellus aquaticus with radium that in this animal the development of the brood pouch is dependent upon the presence of functional ovaries (Haemmerli‐Bovari). The numerous gonad extirpations and transplantations performed on caterpillars by Meisenheimer, Oudemanns, Kope, Prell, and others, do not permit of any certain assumption that hormones exist in these animals. The same is true for experiments with Grillus campestris (Regen). It is nevertheless the opinion of some workers (Harms, von Buddenbrock) that the gonads may be spacially separated from the endocrine organs, as in Courier's experiments mentioned above, and that consequently castration experiments cannot settle the matter.

2. In Physcosoma Harms has demonstrated histologically and physiologically the existence of an endocrine gland (internephridial organ) the secretion of which is essential to the life of the animal.

3. In Cephalopods the morphological characters of the branchial and pericardial glands suggest endocrine action. The fact that tyramine, a product of the salivary glands, has also been found in the blood (Henze, Sereni) is of particular significance.

4. The oenocytes of larval and adult insects, which have been studied by numerous workers, are unicellular endocrine glands. The secretory process originates in the nucleus of the oenocyte. Probably the oenocyte endocrines are of importance in metabolism, and perhaps also in developmental processes such as ecdysis.

5. Koller has shown by blood transfusion that internal secretions are probably concerned in ecdysis and pupation of caterpillars. The place of formation of the hormones concerned is still unknown.

6. Koller and Perkins have shown experimentally that the expansion and contraction of melanin in the chromatophores of shrimps and prawns is due to substances which are secreted into the blood of the animals in response to light stimuli. The seats of formation of the two endocrines are situated respectively in the eyes and in the rostral region of the animals. Koller showed that these substances do not lose their efficacy either by passing through the wall of the alimentary canal or by boiling. This, together with the fact that they are neither specific for species nor for genera, confirms the endocrine nature of the substances in question.

The investigations of Giersberg on the colour changes of Dixippus lead to the assumption of hormone action here also. The sympathetic nerves and the corpora allata are regarded as the places of formation of the substances concerned in the colour change.

7. The feeding of invertebrate animals with vertebrate hormones has not yet led to definite and unambiguous conclusions. Up to the present the experiments are for the most part merely of pharmacological importance.