The nephridium of Protodrilus flavocapitatus is described in detail. With its long-coiled canal and small projecting nephridiostome it is shown to be more complicated than hitherto supposed.
The sperm-duct of the male has a ridged ciliated coelomostome and represents a coelomoduct or possibly a nephromixium. It is argued that the ‘brachynephridia’ and sperm-ducts of all Protodrilids are of the same morphological nature.
The fate of the coelomoduct is related to the mode of emission of the genital products. In the female of Pr.flavocapitatus , which sheds the ripe ova by dropping off posterior segments, the coelomoducts have been lost in all the segments, and in the male in all the segments excepting the eleventh. Remains of the coelomostomes are perhaps represented by the ciliation of the coelomic epithelium in the genital segments of the female. It is maintained that Protodrilus is dioecious, that the female may be early inseminated by the male, that copulation must take place, and that the dorsal glands are perhaps concerned in the process. Ripe spermatozoa only are found in the female, and the so-called stages in ‘cystospermatogenesis’ are probably stages in the phagocytosis of superfluous spermatozoa.
On the Morphological Nature of Genitive Compounds
