RENAL FUNCTION 269 



since it is only in the open, septal, nephridia that such accumulation is ob- 

 served. The pigmented granules are completely absent in the closed in- 

 tegumentary and pharyngeal nephridia. 



With respect to salts Bahl (1945) showed a very active reabsorption 

 of chloride. He added comparative analyses of several other ions in 1947, 

 and the data are of sufficient interest to the task at hand that they have been 

 leproduced in Table 2 of this review. It will be noted that Na, K, Ca, CI, 

 Mg, PO4, and SO4 all are reabsorbed more or less actively. The differences 

 in the handling of these ions is reminiscent of the observations made on 

 other animals, where each ion appears to be conserved in a quantity 

 apparently unrelated to other ions. As a result of the reabsorptive activity 

 the urine is hypotonic to the blood. But perhaps as a result of the passage 

 of some of the urine into the digestive tract, or perhaps through direct 

 uptake of water from the nephridial lumen, the water conservation in this 

 earthworm appears to be better than that of another species which occupies 

 the same habitat during the wet months of the year. In the rainy season 

 individuals of Eutyphocus zvaltoni are found in large numbers in the 

 same soil with Pheretima, but in the dry months Eutyphoeus burrows deep 

 and goes into hibernation while Phcret'nna continues to be active in the 

 relatively dry ground. 



Finally, Bahl found a concentration of creatinine by the nephridium, the 

 urine concentration reaching only 1/5 and 1/7 that of the coelomic fluid 

 and the blood, respectively. He suggests no explanation for this oljserva- 

 tion, which is the reverse of that expected on any analogy to the verte- 

 brate system. Such an active reabsorption of creatinine implies the presence 

 of creatine in the animal, and perhaps the reconversion of creatinine to 

 creatine. So interesting a result warrants further exploration in this group 

 of animals. 



A very interesting addition to the facts adduced by Bahl for Phcret'nna 

 has been made by Ramsay for another earthworm. Using very refined 

 micromethods Ramsay has collected urine from various segments of the 

 nephridia of Lumhricus terrestris which had been quickly removed from 

 experimental animals and kept in frog ringer solution on a microscope 

 stage. By comparing the freezing point of the urine with that of the ringer 

 solution surrounding the preparation, he has shown that the hypotonicity 

 of the urine must originate here — the results do not reveal whether by 

 the reabsorption of organic matter or salt or by the active secretion of water. 

 If the variety of degrees of concentration of ions observed by Bahl also 

 applies to Lnmbricus, the addition of water does not seem a supportable 

 hypothesis ; the reviewer is of the opinion that reabsorption is more likely. 

 Simultaneous measurements of inulin concentration in coelomic fluid, 

 blood, and urine would be helpful ; but the labor of the method is great and 



