SEXUAL ORGANS AND THEIR PRODUCTS IN PHORONIS. 



145 



described by Kowalewskï', not only freely floating in the cœloinic cavity 

 but also contained in the nutriment cells. In P. austral is I have met 

 with the same bodies in the cnelomic fluid, but never in the cells just 

 mentioned ; and in P. ijimai I have simply never and nowhere come 

 across them. They are evidently something of inconstant occurrence 

 and therefore probably of no great physiological importance, so far at 

 any rate as concerns th« discharge of function by the nutriment cells. 

 Another noteworthy point mentioned by Cori is the fact that he found, 

 engulfed in the cells under question, bodies that appeared to him to be 

 the remains of degenerating blood corpuscles. It seems to me that this 

 matter requires confirmation before it can be accepted as a fact. For 

 my own part, I have failed to find any indication whatever tending to 

 support Cori's observations on the point. 



It now lies in order to describe the formation of primary germinal 

 cells. Benham* rightly stated that the sexual products develop from 

 peritoneal cells of contractile capillaries, but the details of the develop- 

 mental process have never become known ; and as to the relation be- 

 tween the generative organs and the nutriment layer, nobody seems to 

 have as yet gone into the matter 



According to my observations, the primary germinal cells begin to 

 appear on a capillary sooner or later after the full development of the 

 nutriment layer. As already indicaded, they arise from, and by prolife- 

 ration of, those small and flat peritoneal cells which remain at intervals 

 at the base of the nutriment layer. This cell-proliferation commonly 

 begins to take place near the base of the capillaries, thence proceeding 

 gradually towards the free distal end. This extension is due to the 

 addition of new cells which have arisen by multiplication of the smal[ 

 and flat peritoneal cells situated on the road of advance. The newly 

 arisen cells — the oogonia or spermatogonia as the casa may be — are 

 nearly uniformly small and approximately spherical in shape ; they form 

 at the region a layer, which is two, three or several cells thick and which 

 is at first covered over by the nutriment layer. 



* Quart. Jour. Miörosc. fc'ci., Vol. XXX, 1S89. 



