No. 2.] THE SPERMATOGENESIS OF LUMBRICUS. 287 



revolves so as to bring the archoplasm into this position. The 

 former is the more reasonable hypothesis. 



The further fate of the archoplasm may be described as 

 follows : the spermatozoon is formed from the spermatid by 

 elongation in the direction of its radial axis. The nucleus of 

 the spermatid, which is here compact and homogeneous, elon- 

 gates, and a tail forms at the distal extremity of the cell (Fig. 

 6). This elongation of the nucleus continues until the spermatid 

 becomes a long columnar cell, with a filament growing out from 

 one end, the other end remaining attached to the blastophore. 

 The archoplasm mass now lies in a vesicle between the tail and 

 the nucleus (Fig. 37). The nucleus and tail elongate still 

 more ; the vesicle disappears by elongation of the archoplasm 

 mass, and the spermatozoon finally assumes the shape of a 

 long rod with a much longer filamentous tail (Fig. 38). 

 This rod consists of middle-piece and nucleus which can be 

 differentiated only by careful staining. The archoplasm 

 mass of the early sperm cells and the middle-piece of the 

 spermatozoon of Ltimbricus are, therefore, one and the same 

 substance. 



The action of acids upon the archoplasm mass deserves 

 further notice. Why should picric acid, for example, reduce 

 the archoplasm from such a structure as that seen in Fig. 43 

 to. that in Fig. 8 in active nuclei, or from such a structure as 

 that seen in Fig, 4 to that in Fig. 41 in resting periods? 

 The condensation here may give some new light on the nature 

 of centrosome structure. It lends support to the view of recent 

 cytologists, that the centrosome is an uncertain and indefinite 

 element of the cell and composed of granules in a greater or less 

 degree of density. 



If, as these observers suppose, the centrosome is but an 

 aggregation of protoplasmic granules, it is easy to conceive 

 that in the archoplasm of Ltimbricus, these granules are not 

 tightly packed, and that a favorable fixing agent will preserve 

 them in this condition. Such a result is given by the use of 

 Hermann's fluid on teased specimens. If a killing agent is 

 used which does not act so quickly as the platino-osmic-acetic 

 mixture, it is conceivable that a condensation of the granules 



