spermatogenesis of the Mongoose, etc. 167 



sphere seems to have arisen directly from the idiosome by process of vesic- 

 ulation and rejection of one or several small plastin particles. The con- 

 densing nucleus moves into an elongating projection of the cell, and then to 

 and beyond the periphery (figs. 16 and 17). Meanwhile the "sphere" has 

 flowed backward over the elongating nucleus, its lateral limits being marked 

 by a distinct line for some distance on either side of the growing axial fila- 

 ment. The filament is marked proximally by two granules (the products 

 of the original centrosome, fig. 15), the anterior one at the point of attach- 

 ment to the nucleus, the posterior one passing along the axial filament as 

 the "ring centrosome" (figs. 17 and 18) to the posterior end of the middle 

 piece. At the later and adult stages the middle piece is attached to the 

 head by a delicate neck (fig. 20, drawn in the living condition), in which 

 appears a knob, the proximal centrosome, or "end knob" (figs. 19 to 21). 

 The posterior limit of the middle piece is defined by the termination of the 

 spiral filament. The latter arises by a coalescence of mitochondria included 

 within the limits of the backward-extending sphere (middle piece). The 

 remaining mitochondria fail of inclusion and are cast off with the discarded 

 cytoplasm. This observation, made also in a number of other forms 

 (e. g., opossum. Jordan, 1911; Euchistus, Montgomery, 1912), invalidates 

 any hypothesis attributing specific hereditary significance to mitochondria. 



CAT. 



The later steps In the spermatogenesis of the cat, including the spermatid 

 and subsequent stages, have recently been described by Leplat (1910). 

 As to the prespermatid stages, it may be said in brief that they are essentially 

 similar to those described for mongoose, and no convincing evidence appears 

 at any stage of heterochromosomes. Respecting the postspermatid stages 

 also, the similarity amounts practically to an identity; and my own obser- 

 vations on these stages agree essentially with those made and illustrated by 

 Leplat. 



More recently Gutherz (191 2) has described and illustrated (in two 

 figures) first spermatocytes of the cat stained both in the iron-hematoxylin 

 and the Biondi mixtures. His conclusion confirms my own as to the 

 probable absence of heterochromosomes. However, he figures a synaptic 

 (synizesis) and a postsynaptic stage in which appear heterochromosome- 

 like elements in iron-hematoxylin preparations. The true acidophile 

 nature of these bodies, however, is revealed in the Biondi material. On 

 the basis of this observation he casts doubt upon the interpretation as a 

 heterochromosome of the element described by Winiwarter and Sainmont 

 in their iron-hematoxylin preparations of the oocyte of the cat. I can only 

 add that my material (also stained with iron-hematoxylin) reveals elements 

 somewhat similar to those described and illustrated by Gutherz for the 

 first spermatocytes, but which, on grounds of morphology, location, relation 

 to spireme, and general behavior, I can not interpret as typical X-elements. 

 Moreover, in well-decolorized preparations their non-chromatic nature is 



