GERM CELLS IN PEDICELLINA AMERICANA 49 



and female germ-cells are quite alike. Further, the several 

 complicated changes which finally lead to the formation of 

 the figures of the maturation divisions, as well as these divisions 

 themselves, are in both instances quite identical. Under such 

 conditions as these it is clear that, whatever be the different 

 roles which the egg and the sperm play in development, they 

 are, at bottom, morphologically equivalent and diverge only 

 secondarily in adaptation to their respective functions. We 

 may at the present day appropriately conclude with the words 

 of the classic study of Oskar Hertwig : *' Vergleich der Ei-und 

 Samenbildung bei Nematoden " : Eibildung und Samenbildung 

 sind zwei einander nahe stehende Processe ; sie gehoren soeng 

 zusammen, dass die Kenntniss des einen nothwendiger Weise 

 auch das Verstandniss des anderen fordern muss, sofern man 

 nur durch Vergleichung die gegenseitigen Beziehungen festzu- 

 stellen sucht." 



Summary. 



1. In Pediccllina americana^ the polypides are of separate 

 sexes, but bpth male and female individuals may occur on the 

 same stolon. 



2. The ovaries and testes are bilaterally symmetrical organs. 

 Unlike the testes, where the germ cells are irregularly dis- 

 tributed, in the ovary, a continuous line of development of the 

 egg cells can be traced from the center outward. 



3. The processes of oogenesis and spermatogenesis are, in 

 general, quite identical. 



4. In young male and female polypides, the primary egg and 

 sperm cells lie nearest the oviduct and spermduct respectively, 

 and give rise through mitosis to the several generations of 

 oogonia and spermatogonia. 



5. With the exception of the last generation of spermato- 

 gonia, the chromosomes are V-shaped, as are those of the tissue 

 cells. The normal number of chromosomes is very probably 

 twenty-two. 



6. In the last generation, they appear as dumb-bell shaped 

 rods and have arisen by the opening-up of the angle of the 

 former Vs. 



