NITROGENOUS EXCRETION 51 



excretes nitrogen at a high rate, mainly as protein, until the piece 

 dies. 



Urine as excreted from the earthworm body is acidic. The 

 acidity is shown to vary from time to time and starving animals pro- 

 duce less titratable acid than do feeding worms. E. foetida produces 

 more acid than does L. terrestris, but whereas the pH of the urine 

 is buffered by urea in the case of L. terrestris, as shown by a rise 

 in pH upon treatment with urease, this is not so in E. foetida. 

 Needham (1957) suggests that in the latter case the buffering of 

 the urine is a function of some non-nitrogenous akali, citing as a 

 possible mechanism the calcium carbonate removed from the 

 calciferous glands. 



Thus in these two related species the excretory products differ 

 in a number of ways. E. foetida has a much higher specific output of 

 total nitrogen and of the ammonia fraction than does L. terrestris 

 and ammonia makes up a larger part of the total excreted. The 

 ammonia excreted does not go down, but rather goes up, when the 

 animal is subjected to fasting. E. foetida has a higher removal of 

 acid, and it is beHeved utilizes a non-nitrogenous base to neutralize 

 it, possibly the calcium carbonate from the calciferous glands, 

 which is thought to be playing a part in the internal regulation of 

 pH as well (Voigt, 1933). In the conditions of Needham's 

 experiments the anal and nephridial excreta were able to mix 

 freely, and thus his explanation might be true for this set of 

 circumstances, but in the field the animal is free ranging in a 

 burrow, and as it is probable that urine from the nephridia is 

 immediately absorbed on to soil particles as it is released, it seems 

 unlikely that concretions issuing from a distant site will have much 

 effect upon the urine pH. 



Cohen and Lewis (1949b) and Needham (1957) provide clear 

 demonstrations as to variations in excretory products of earth- 

 worms when they are starved, although they do not agree on the 

 amounts involved. That the geographical location may be impor- 

 tant in arriving at results and conclusions seems to be indicated by 

 the work of Haggag and El-Duweini (1959). A. caliginosa excretes 

 nitrogen in a pattern similar to that of L. terrestris (Needham, 1957) 

 though the absolute amounts are much smaller. In Egyptian 

 representatives of this species protein accounts for up to 50% of 

 the total nitrogen excreted, similar to that reported by Needham. 



