?A2 E. M. NELSON OV THE HUMAN SPERMATOZOON. 



that part of the head of the young mushroom which eventu- 

 ally becomes the periphery of the fully grown head breaks 

 away from the stem it leaves a ring round the stem with 

 more or less fragments of the edge of the head adhering to it. 

 We shall find our analogy to this in what I have termed the 

 calyx of the spermatozoon. 



Our ignorance with regard to the nature of the spermatozoon 

 is proved by the paucity of names we have for its various parts. 

 A machine capable of making a watch is necessarily very com- 

 plex ; but that a machine which shall make a watch capable 

 of making another watch must be much more complex has been 

 pointed out by Pale}*. A watch-making machine we know 

 all about, and there is a whole vocabulary of names for its 

 various parts. What shall we say, then, for that which by 

 parity of reasoning must be the most complex of all complex 

 machines ? I fear that three names will exhaust all that has 

 hitherto been known about it, viz., a head, a tail, a nucleus. 

 Xow, however, I hope to increase this vocabulary. 



To begin with, the head, which I have called the spore, has 

 not been, to my mind, correctly figured hitherto. 



Viewed in its flattened aspect its anterior end is very blunt, 

 not unlike the point of a table knife. 



In outline it is like an egg, the posterior part towards the 

 tail being the small end. In all the drawings I have met with 

 the reverse of this is represented. The edge view shows that 

 it is very slightly concave on its under and convex on its upper 

 side. It is therefore something like the half of a converging 

 meniscus seen in section. 



The spores vary slightly in size, but I regard the large end of 

 an egg view of the flat side an unmistakably constant feature. 



The spore fits into a cup just as an egg or an acorn fits into 

 a cup ; the small end of the egg being in the cup. When on 

 the flat that portion of the spore which is exterior to the cup 

 is often broader than the cup. 



The outline of the head has always been represented as 

 unbroken, but the edge of the cup can be distinctly seen both 

 in front and side views. 



At the bottom of the cup there is what I have termed the 

 calyx. This is exceedingly variable, sometimes it is absent, and 

 sometimes half the size of the whole spore. Figs. 9 and 10, Plate 



