Some Points in the Spermatogenesis of Mammalia. 159 



the rat correspond, either singly or together, to tliese „Intermetliären 

 Knötchen" there seems to be not tlie slightest doubt; and the existence 

 of this structure in the young mammalian spermatid is, in itself, 

 interesting, because when the cell l)ecomes adult i have not been' able 

 to ditïerentiate it with certainty; and, as Ballo witz seems only to have 

 found it in two species, the question naturally arises, in Iiow many 

 more would it be visible in the younger stages of development? Which 

 of the two kinds of intermediary bodies present in the developmg 

 spermatids of the rat corresponds to those figured by Ballo witz, it is 

 quite impossible for me to say. 



Ballowitz left the origin of these structures unsolved, and I am 

 not aware that any history has been ascribed to them by other 

 authors; hut my own preparations suggest strongly that in t/ie rat. 

 the tivo laterally disposed structures are the final expression of fhf 

 spermatid centrosom.es. At this stage in the spermatid metamorphosis 

 there exists, in the cell protoplasm a differentiated area in relation to 

 the nuclear head, which extends in the form of a blunt cone from the 

 level of the Cercosome to the extremity of the supporting flap; its 

 narrower end sits in, and completely fills the shallow nuclear cup afore 

 described (Fig. 25 i). The protoplasmic contour of the great body of 

 the cell is extended, in the direction of the nucleus, beyond this diffe- 

 rentiated cone, and it assumes the form of a blunt enlargement 

 (Fig. 25). The delicate wall of this enlargement becomes continually 

 more bulged out, until it assumes the appearance of a blunt overhanging 

 bag (Figs. 26, 27, 28). At the bottom of this bag a dense mass (/') 

 becomes differentiated, but it does not appear to have any definite 

 value, as it vanishes in the succeeding phases. 



During the formation of this sack- like enlargement of the shaft 

 of the spermatozoon the spermatid centrosomes are displaced (Fig. 27 c), 

 and they become finally so closely applied to the large head of the 

 spermatozoon that it becomes impossible to follow their history further. 

 The difficulty of so doing is enhanced by the growing refi-activity of 

 the spermatic shaft or „Hauptstück" in which they are contained. It 

 will be seen also that there is no representative of the „Mittelstück'' 

 of authors, unless the intermediary bodies be together considered as 



