196 ORGANISED FLUIDS. 



diminish; the seminal animalcules are well grown and lie 

 bent up within the cyst ; their spiral ends are more con- 

 spicuous. The delicate covering (involucrum) is now drawn 

 more closely around the bundle of spermatozoa it includes, 

 and where it covers their spiral ends anteriorly it assumes 

 a pyriform outline (see Plate XYI. Jig. 2. i), and at the 

 opposite extremity is perhaps at this time open ; but it is 

 difficult to speak decisively on this point. The cysts are 

 now very commonly bent nearly at right angles or like 

 knees, but at length they appear stretched out and straight, 

 and have attained their full size. (See Plate XVI. fig. 2. k.) 

 The capsules of these vesicles are at all times, and especially 

 towards the end of their existence, highly hygroscopic ; the 

 addition of a little water causes them to burst, the masses 

 of spermatozoa rolled up like a little skein of thread or 

 silk escape, and occasionally at this stage exhibit motions 

 individually, which, however, whilst the animalcules continue 

 in the ducts of the testes, are frequently not to be observed, 

 and are never either general or remarkable. The sperma- 

 tozoa, after the rupture of the cyst, advance in freedom to 

 the vas deferens." * 



The process Wagner states subsequently to be precisely 

 similar in man and the Mammalia, although it is more 

 difficult to follow it in them. 



The accuracy of the above account of the development 

 of the spermatozoa has been admitted by most other ob- 

 servers in all respects save one important one : thus 

 Kcelliker has shown that the evolution takes place in the 

 included or secondary cells, and not, as Wagner describes 

 it, in the spaces between these, a single spermatic animalcule 

 being formed within each ; the granules inclosed in these cells 

 disappear gradually as the spermatozoon assumes a definite 

 form, and Krelliker further supposes that these granules 

 constitute by their union with each other the substance 

 of the spermatozoa which escape from both the secondary 

 and primary cells by the rupture of their investing mem- 



* Translation of Wagner's Elements, by Willis, pp. 25, 26. 



