8 



The Unity of the Organism 



of delicate filaments attached to the nuclear membrane. The 

 proximal ends of these arise in a circle around the basal end 

 of the nucleus with the centrosomes as a center^ while their 

 distal ends project freely into the cytoplasm." ® (figure 40 c.t.f.) 

 These filaments "are at first very short and thin^ but they in- 

 crease in length and thickness rapidly. By the progressive dif- 

 ferentiation of the cytoplasm between them they soon fuse into 

 a hyaline tube, surrounding the axial thread and open at its lower 

 extremity." (figure 41, c.t.) The capital point is that we have 

 here a well-defined structure the development of which is in- 



an 



FIGURE 41. SPERMATID OF FUR SEAL ( AFTER OLIVER). 



h.c, head cap. c.t., caudal tube, an., annulus. 



dubitably proved to depend primarily on parts of the cell other 

 than the chromatin. Indeed no one, apparently, has pretended 

 that the chromatin takes a part in its production, for even those 

 investigators who have not believed that it arises from the cyto- 

 plasm alone have held that it originates from the membrane of 

 the nucleus. 



About the chromatoid body (5) and the "spindle remnant" (6) 

 (figure 37) J, little need be said in this connection as they seem to 

 be inconstant structures the significance of which is in much 

 doubt. Finally, mention should be made of the fact that a con- 

 siderable portion of the cytoplasm is cast off entirely in the 

 ontogeny of the sperm of many animals, as for example the seal, 



