56 



KARM NARAYAN BAHL 



2. If they are ectodermal, how do the septal nephridia with 

 their ducts come to lose all connexion with the body- wall 

 and be associated with the septa and the gut, which are meso- 

 dermal and ondodermal structures respectively ? 



3. Is the adult condition of nephridia preceded by a ' mega- 

 nephric ' or paired condition in the embryo ? 



4. If so, how is the adult condition derived from the em- 

 bryonic condition ? 



5. Do facts of development throw any light on the phylogeny 

 of the Oligochaete nephridial system ? 



3. The Cocoon. 



The egg-capsules or cocoons of Pheretima do not differ 

 in any essential particular of structure from those of Lum- 

 bricus, Allolobopliora, or Acanthodrilus, pre- 

 viously described by Vejdovsky (16) and Beddard (3) ; but 

 I am recording here my observations on the cocoons of this 

 worm to bring out their special characters. 



I have no observations to offer on the mode of formation 

 of this structure in Pheretima, but I have no reason to 

 doubt that it is formed in much the same way as in all the 

 other genera where cocoon-formation has been carefully 

 studied, and that the clitellum alone is concerned in its pro- 

 duction. 



^ Although the cocoons vary somewhat in size, they are very 

 much smaller than those of Lumbricus. On an average 

 they are about 1-5 to 2 mm. by 1-8 to 2-4 mm., i.e. about 

 one-third the size of the cocoons of Lumbricus. 



The cocoons are light yellow or olivaceous in colour, the 

 empty cases having a clear transparent olive colour. In form 

 they are more or less rounded in shape and give a distinctly 

 swollen appearance, the two ends being drawn out into very 

 short fibrous appendages. 



My observations on the time of egg-laying are based on two 

 species of Pheretima, namely P. post hum a and 

 P. rodricensis. The cocoons of the first species were found 

 by me at Allahabad (India) in spring and summer months 



