THE SPERMATOGENESIS OF LUMBRICUS. 



GARY N. CALKINS. 



The spermatogenesis of the earthworm is characterized, in 

 its external features, by a number of peculiarities which have 

 not yet been brought into relation with the more usual types. 

 The only published work on the subject is by Bloomfield ('80), 

 who gave a fairly accurate account of the external features, 

 drawn chiefly from living specimens or from glycerine prepara- 

 tions, but he failed to make out the internal changes undergone 

 by the developing cells. Bloomfield' s principal results may be 

 briefly summarized as follows: (i) The early germ cell is not 

 entirely used in the formation of spermatozoa ; a central part 

 remains passive and serves to carry the developing spermatic 

 cells. This central part is called the sperm blastophore and 

 may or may not be nucleated. (2) The sperm blastophores in- 

 crease by division while in the testis, and disappear, probably by 

 atrophy, after the spermatozoa leave them. (3) The blasto- 

 phore corresponds to the nucleated supporting cells (Sertoli 

 cells) of the frog and salamander. (4) The large nucleus of the 

 early sperm cell divides many times to form "secondary" nuclei 

 which " stand out around the central mass or blastophore of the 

 generating spheroid with very little protoplasm clothing them." 

 These nuclei become the rod-like heads of the spermatozoa. 

 (5) The protoplasm collects in a small " cap or knob-like mass 

 at the distal end" of the developing cell, and from this grows 

 out the long vibratile tail of the spermatozoon. (This "mass" 

 must be the archoplasm of the spermatid.) 



The present investigation was first undertaken in the hope 

 of explaining the significance of the "sperm blastophore" and 

 of identifying the various stages of spermatogenesis in accord- 

 ance with the usual terminology. It soon became apparent 

 that Liimbriais is an especially favorable form for tracing the 

 origin of the various parts of the spermatozoon, and especially 

 the history of the archoplasm, and to this division of the sub- 



