518 SPEKMATOZOA. 



which appear to affect their organization. Strychnia, opium, and hy- 

 drocyanic acid likewise stop their motions, but without causing any 

 change in their form. 



The production of spermatozoa is best studied in the case of birds. 

 Spermatozoa For this purpose Wagner recommends that one of the order 

 in birds. of Passeres be taken in the pairing time. The condition of 

 the testes indicates the state of evolution of the spermatozoa. In win- 

 ter those organs are of the size of a pin's head, but in spring they have 

 increased twenty or thirty fold. Exteriorly they exhibit convolutions like 

 those of the brain, and contain granules and seminal globules. After 

 pairing time is over, they relapse to their original diminutive state. The 

 seminal globules appear to be derived from the epithelial cells lining the 

 tubuli seminiferi. They are developed into what are termed primary 

 cells, each of which contains a number of secondary cells or vesicles of 

 evolution. In the interior of these vesicles the spermatozoa originate, 

 as a derivation or development from the nucleus, each vesicle giving rise 

 Evolution of to one spermatozoon. When this has reached perfection, the 

 spermatozoa, vesicle deliquesces and sets it free. There are from one to 

 twenty vesicles of evolution in each primary cell. In birds the filaments 

 may be retained for a length of time in the primary cell after deliquescence 

 of the vesicle, but in mammals, as soon as the filament is mature it es- 

 capes. In the former case the filaments aggregate into bundles, but they 

 break up into individuals when the primary cell deliquesces. 



24L Fig. 247, spermatozoic filaments, develop- 



ing in Certhea vulgaris : #, seminal granule ; 

 , cyst, with two vesicles of evolution, many 

 granules, and a bundle of spermatozoa ; , oval 

 cyst, with spermatozoa coiled up. (Wagner. ) 

 Of the formation of spermatic filaments 

 Dr. Burnett gives an account somewhat dif- 

 ferent from the preceding. According to him, 

 "the morphological changes in the sperm- 



Development of spermatozoa. ^ preceding the formation of the Spermatic 



filaments are identical in their character with the changes in the ovum 

 which are antecedent to the formation of the new being. When the gen- 

 erative function begins to be developed, the character of the epithelial 

 cells lining the tubules is modified. The cells pass to a higher degree 

 in function, but do not undergo any change in structure, except a slight 

 increase in size. In this condition they divide and subdivide, by a pro- 

 cess similar to the segmentation of the yolk, until they are entirely con- 

 verted into a mulberry mass. A liquefaction of the segmented contents 

 into a minute granular blastema then ensues, and from this the spermatic 

 filaments are developed. In the Plagiostomes, Dr. Burnett was able to 



