[Morphology of adult and sub-adult Wuchereria bancrofti.  Differential characteristics among the strains]. 
The description of the fourth stage larva of W. bancrofti provides an indication of the direction of morphological evolution in the genus showing in particular that W. kalimantani is more highly evolved than W. bancrofti and constitutes a "capture" by Presbytis of the species parasitic in man.  No morphological character of adult W. bancrofti distinguishes the geographic origin of the different collections studied.  By contrast, the morphological characters of the microfilariae and their biological features are significantly different, but are not inter-correlated.  It therefore appears that in the genus Wuchereria, as in the other viviparous filarioids, the phenomenon of speciation is evident first of all in the morphology of the microfilaria, the stage most susceptible to selection pressures.