DEGENERATION OF INTERNAL ORGANS 239 



layer (compare the description of Lumbricilliis maximus above). I was there inclined to 

 ascribe the appearances to excessive parasitization of the alimentary canal, though I had 

 to confess that in some specimens of extreme degeneration there was no evident parasiti- 

 zation. 



Yet more recently I have again come across examples of degeneration in Enchy- 

 traeids ; some small worms belonging to the genus LumbriciUus sent to me from Plymouth 

 by Mr J. S. Colman proved to be specifically indeterminable, owing to a wholesale 

 degeneration of the organs — not the genital organs only, nor the alimentary canal only. 

 Specimens that I have since received from Mr Colman, at a different time of the year, 

 have given me no trouble, and I hope shortly to describe them as a new species, 

 L. pumilio. I think the condition here is probably a post-maturity degeneration (v. 

 infra) — which, however, has spread beyond the genital organs and affected the whole 

 body. 



Mrazek (19 10) found that after keeping for some time in unfavourable conditions, 

 Tubificids showed in the coelomic cavity what he took to be portions of the longitudinal 

 muscular layer, sometimes in large amount, so that the coelom was full of this material ; 

 the fragments are sometimes engulfed by the amoebocytes of the cavity. The genital 

 organs were degenerating at the same time, but Mrazek does not connect the two 

 degenerations. 



I might also recall the fact that in the Naididae there is sometimes a degeneration of 

 the alimentary tract at the height of sexual maturity (in the genera Nais, Dero, Hae- 

 monais;ci. Stephenson, 1930, p. 131, and references there) ; but in these worms the other 

 organs are intact. 



I think my first acquaintance with these degenerations was many years ago, when I 

 was working in India, and received from Burma, through the Indian Museum, a number 

 of Enchytraeids which had been found attacking rice, burying themselves in and living 

 in the shoots ; an identification was therefore of some economic interest. However, I was 

 unable to say anything, except to make a request for more material, taken, if possible, at 

 a different time of the year. I subsequently received a second consignment ; but here 

 again the same condition was present, and I was unable to do anything with it. I have 

 no doubt that the Agricultural Department, which sent the worms, thought I was a 

 particularly incompetent worker. 



That the genital organs of Oligochaetes undergo regression after the period of sexual 

 maturity is well known ; the changes include the production of large numbers of phago- 

 cytes, and the disappearance of the sexual organs by phagocytosis. That the spermatozoa 

 remaining in the seminal vesicles or free in the testicular segments are ingested by 

 phagocytes is familiar to us mainly from the work of Cognetti (191 1, 1930) and 

 Cernosvitov (1930); for an account of the histological changes in the degenerating 

 organs, and their disappearance by phagocytosis, we are dependent on Cernosvitov 

 (1930 a), who describes these processes in Tubifex. 



To which of these forms of degeneration the phenomena described in the present 

 paper are to be assimilated it is difficult to say. They can here hardly be due to parasiti- 



