284 CALKINS. [Vol. XI. 



cells to a position at the extreme tip of the spermatozoon, 

 whereas in \\iQ fertilization of the echinoderm Q.gg Wilson ('95) 

 and Mathews ('95) have shown beyond question that the sperm 

 center originates from the middle-piece. In the fertilization 

 of the Q-^Zi and in the spermatogenesis of Limibriais, however, 

 the results of different observers agree. In the fertilization of 

 the Limtbrictis egg Foot ('94) has shown that the sperm center 

 probably arises from the middle-piece, and in the spermato- 

 genesis of Liimbriais I have shown that the archoplasm is a 

 continuous element of the cell and forms ultimately the middle- 

 piece of the spermatozoon ('94). 



Many other investigators besides Field have followed the 

 course of the centrosome from the early sperm cells to the 

 anterior end of the spermatozoon, but in most cases the fertili- 

 zation of the eggs has not been studied. Flemming ('88) in 

 the spermatogenesis of the salamander was in doubt as to the 

 origin of the extreme tip of the spermatozoon, but thought that 

 the middle-piece originated from the chromatin. Platner 

 ('85, '89) showed that the extreme tip of the spermatozoon in 

 butterflies and in some pulmonates {Helix poviatia and Litfiax 

 agrestis) is formed from the centrosome. Benda ('9i) showed 

 that in the spermatozoa of mammals, birds, and reptiles, the 

 ^^ archiplasma'" forms the Spitzenknopf and Kopfkappe, and 

 Moore ('94) asserted that in rat spermatogenesis a portion of 

 the archoplasm (archosome) forms the anterior tip of the sper- 

 matozoon, but that the place of the Mittelstiick "is apparently 

 occupied by the spermatid centrosomes and an intermedidr 

 KorpercJien " 



A possible explanation of some of these differences may be 

 that in many cases the ^^ Ncbenkcrn" is confounded with the 

 archoplasm, and that the extreme tip of the spermatozoon is 

 formed from this or from a portion of it, instead of from the 

 centrosome and archoplasm. Henking ('9i) showed that in the 

 spermatozoon of PyrrJiocoris aptenis the tip of the sperma- 

 tozoon is formed from a part (Mitosomd) of the Nebenkern. 



I have found two peculiarities in the archoplasm of Ltim- 

 bricics due to treatment of the preparations. First in prepara- 



