THE RELATION BETWEEN AMITOSIS AND MITOSIS. 2O3 



more puzzling. The most careful examination, under varied con- 

 ditions of fixation and staining, of spermatozoa in the male ducts 

 and in the seminal receptacle of the female ducts, which becomes 

 greatly distended with them at a certain stage, failed absolutely 

 to reveal the existence of a head differing in appearance from the 

 tail. The examination and staining of fresh spermatozoa from 

 the seminal receptacle and ducts of living proglottids led to the 

 same result. The spermatozoa appeared as very long thread- 

 like structures perhaps slightly larger at one end than at the other 

 but without the least trace of a physically or chemically differen- 

 tiated head. 



Then the question arose as to whether the eggs were actually 

 fertilized by these spermatozoa. As will be described in the fol- 

 lowing paper, the spermatozoa were found entering the eggs as 

 these passed the opening from the seminal receptacle on their 

 way to the uterus, and nuclei which could be nothing else than 

 male pronuclei unless these eggs differ from other known cases 

 in their maturation and fertilization stages were found. Return- 

 ing to the developing spermatozoa the most careful study was 

 made of the various stages and especially of the masses like Fig. 

 49 (PI. XV.) which were apparently undergoing degeneration. It 

 is very difficult to distinguish details in these masses for they 

 stain more deeply as they condense and the nuclei especially 

 become more or less filled with deeply staining granules and 

 masses. In the course of time certain apparently favorable cases 

 were found some of which are shown in Figs. 48, A-^S, C (PI. 

 XV.). These seem to indicate that the "head" of the sperma- 

 tozoon, /. e., the part arising from the nucleus is formed from the 

 two nuclear granules, the peripheral and the other which may be 

 central or proximal, together with the connecting strand, and 

 furthermore, that when degeneration of the other parts of the 

 nucleus begins the spermatozoon is set free. Figs. 48, ^-48, C, 

 show examples of the early stages of nuclear degeneration in 

 sperm cytophores. In Fig. 48, C, the spermatozoon head is 

 apparently in the act of escaping from the degenerating nucleus. 

 The peripheral portion of the nuclear membrane has disappeared 

 but the peripheral nuclear granule is still recognizable. Figs. 

 48, A, and 48, B, are apparently somewhat earlier stages in 



