No. 2.] THE SPERMATOGENESIS OF LUMBRICUS. 275 



been subjected to pressure, when the filament cells or sperma- 

 toblasts will be squeezed asunder, but remain connected with 

 the central substance by fine strands of protoplasm. This 

 central mass is the blastophore." 



My observations confirm Bloomfield's in regard to the origin 

 of the blastophore, but his description is so meager that a 

 further account will not be superfluous. 



These "cushions" with their developing cells (spermato- 

 spheres) can best be studied in teased specimens. They are 

 frequently of fantastic shape (Fig. 5), a condition which led 

 Bloomfield to suggest a normal increase by division of the 

 entire blastophore. They become spherical during the later 

 stages of spermatogenesis, especially during the metamorphosis 

 of the spermatid. 



A testis of Ltimbriais in section exhibits numerous ellip- 

 soidal and multinucleate cells (Figs, i and 2). The number of 

 nuclei in these cells is inconstant, varying from one or two to 

 as many as twenty, and at this stage they are distributed 

 through all parts of the cell, in the center as well as at the 

 periphery. A study of the various forms shows that the 

 single nucleated cell represents the earliest germ cell, which, 

 by repeated division of its nucleus, gives rise to the multi- 

 nucleated form. Division figures are frequently seen, and it is 

 a curious fact that in whatever stage of maturation a group 

 may be, the nuclei are all in the same stage of activity at the 

 same time (Figs. 5, 12, and 43). 



The multinucleate cells pass from the free edges of the 

 testes into the seminal vesicles, and sections of the latter show 

 that changes in the distribution of the nuclei have taken place. 

 They no longer lie without order in the cell but are arranged 

 around the periphery like the nuclei of an arthropod Qg^ 

 (Fig- 3)- The resemblance to the centrolecithal ^gg is even 

 more striking as development continues, for cytoplasmic cleav- 

 age occurs later around each nucleus (Fig. 4), thus differentiat- 

 ing the blastophore from the germ cells. These cleavages 

 deepen until the attachment of the germ cells to the blasto- 

 phore is reduced to a thin film of cytoplasm. The blastophore 

 remains non-nucleated throughout. 



