140 



THE GERM-CELLS 



connection with which, may be developed secondary or accessory fila- 

 ments and other structures. At the tip the axial filament may lose 

 its envelope and thus give rise to the so-called "end-piece" (Retzius). 

 In Trito)i, for example (Fig. 66, /• ), the envelope of the axial fila- 

 ment ('* ])rincipal filament ") gives attachment to a remarkable fin-like 

 - — - membrane, having a frilled or 



^ — ■'■■- 



-/6 



\ 



7 



ft 





undulating free margin along 

 which is developed a "mar- 

 ginal filament." Toward the 

 tip of the tail the fin, and 

 finally the entire envelope, 

 disapj)ears, leaving only the 

 axial filament to form the end- 

 piece. After maceration the 

 envelope shows a conspicuous 

 cross-striation, which perhaps 

 indicates a spiral structure 

 such as occurs in the mam- 

 mals. The marginal filament, 

 on the other hand, breaks 

 up into numerous parallel 

 fibrillar, while the axial fila- 

 ment remains unaltered (Bal- 

 lowitz). 



A fin-membrane has also 

 been observed in some insects 

 and fishes, and has been as- 

 serted to occur in UKinimals 

 (man included). Later ob- 

 servers have, however, failed 

 to find the fin in mammals, 

 and their observations indi- 

 cate that the axial filament is 

 merely surrounded by an 

 envelope which sometimes 



Fig. 68. — Spermatozoa of mammals. {A-Fixom showS traCCS of the same 

 Ballowitz.I . , , 



, „ , „• • N „ ^, c sj3n-al arrangement as that 



A. Badger (living). /?. The same after staining. ' . ^ . 



C.'^A\. {Vesper ago). Z^. The same, flagellum and which is SO COUSpicUOUS in 



middle-piece or connecting-piece, showing end-knobs. 4-Uq COnnectin<^^-Diece In the 



E. Head of the spermatozoon of the bat {Rhino- ^i u a\ 



lophus) showing details. F. Head of spermatozoon SkatC the tail has tWO hla- 



of the pig. G. Opossum (after staining). //.Double mcntS, both COmpOSCd of 



spermatozoa from the vas deferens of the opossum. n i /~i -n . i i 



/ R^^^ parallel nbnlloe, connected by 



h.c. head-cap (acrosome) ; >(•. end-knob ; w. mid- a membrane and Spirally 



dlffe'^rem'par'tsr''"' ^'" ^' ^' ^' '""''"''"^ ^^ ^'^^ V.^\^l^^ about cach Other; a 



