54 KARM NARAYAN BAHTi 



scolides australis, and by Bourne (8) in Mahbenus 

 i m p e r a t r i X and P e r i c b a e t a p e 1 1 u c i d a . 



The earthworm Octochaetus (Acanthodrilus) pos- 

 sesses, in the adult condition in the interior of its body, eight 

 tufts of nephridia in each segment, but a much larger number 

 of external orifices for these nephridia. The funnels are present 

 on these nephridia in the hinder region only and not in the 

 anterior region (4). During development, according to Beddard 

 (3), the embryo possesses a paired series of organs in each 

 segment, which, as Vejdovsky thinks, are probably the equiva- 

 lents of the pronephridia of Lumbricus. These paired 

 nephridia of the embryo are, however, provided with well- 

 developed ciliated and functional nepln'ostomes. 



Beddard was not able to follow these paired nephridia to the 

 condition obtaining in the adult, and his work is very incom- 

 plete ; but he thinks that the nephridia of the embryo are 

 converted into those of the adult, firstly by a temporary 

 cessation of function (?) in a part of the nephridium — the por- 

 tion nearest the funnel — which is produced by the disappear- 

 ance of the lumen, and secondly by the active growth of this 

 part of the nephridium, as well as other parts, and by the 

 formation of a fresh series of apertures to the exterior. 



Our knowledge of the development of nephridia in the 

 Australian earthworm Megascolides is fairly complete. 

 In the adult condition of this worm the diffuse network of 

 minute excretory tubules is reinforced by the existence of 

 larger paired tubes, one pair to each segment ; and these large 

 paired nephridia appear to be in connexion with the smaller 

 tubes. We have, therefore, both the ' meganephric ' and the 

 ' plectonephric ' systems existing side by side in the same 

 worm. Vejdovsky (16) has found that ' in this worm also, 

 during development there is to begin with a pair of nephridia 

 to each segment ; these have a fuimel, and from the fuimel 

 leads a straight duct not perforate ; here and there the cells 

 become larger and finally form loops ; these loops ultimately 

 increase in size and become comphcated coils, the comiective 

 point of the original tube degenerating into a mere strand of 



