164 J- Moore, 



some advances in front of the spermatazoon head during- fertilisation; 

 and we may ask, what does the archosome, the little body at the 

 cephalic apex of the rat's spermatozoon, do? 



It comes to this, in mammals, after an archoplasmic metamorphosis, 

 (assuredly not introduced for nothing) a small body (archosome) is 

 sifted out, and incorporated into the cephalic apex of the spermatozoon. 

 There is no „Mittelstück", but its position is apparently occupied by the 

 spermatid centrosomes and an „intermediar Körperchen". Either the 

 archosome represents the archoplasm in the spermatozoon, (i. e. it is 

 equivalent to Field's Nebenkern, to the Nebenkern in Amphibia, to 

 the „Mittelstück") and has changed places, being in an extreme instead 

 of a mean position, or it stands for the "spermocentre". Observations 

 are wanting to decide between these two suppositions, but probability 

 makes entirely for the former. I see no virtue in the position of 

 these parts, and the fact that bodies answering to the spermatid 

 centrosomes exist in mammalian spermatozoa seems to be almost con- 

 clusive that the archosome is equivalent to the Nebenkern or the 

 „Mittelstück". 



Much of the recent work seems to be a confirmation, on the 

 animal side, of Strasburger's supposition that a representative of the 

 cytoplasm is essential to the proper fertilisation (of plants). In what 

 way is it necessary then? There is no lack of cytoplasmic material, 

 as a rule, in ova. The fact that in the more specialized spermatozoa, 

 such a small speck of this substance is actually carried in, seems to 

 suggest that in these forms, a process of reduction had been carried 

 to a minimum beyond which it is impossible to go. Julin supposes the 

 distinction between the sperm-cell and the ovum to reside in the 

 existence in the former of the "spermocentre", wherewith it stirs up 

 mitotic-action and segmentation in the latter. It is not true however 

 for all ova as my friend Mr. Wheeler has recently found centrosomes 

 in the unfertilized ova of Myzostoma glabrum. This is quite possible, 

 but the supposition that the "spermocentre" is the only cytoplasmic 

 constituent, (if it is a cytoplasmic constituent) necessary to the sper- 

 matozoon, will not hold for a moment, since in spermatozoa like those 

 of mammals and echinoderms both centrosomes and cytoplasmic con- 



