THEIR NATURE AND FUNCTION. 43 



included in the cavity of the parent cell ; so that the process is in all 

 essentially the same as that already described as occurring in mammiferous 

 animals. The smaller vesicles, within each of which a filament is formed, 

 and which sometimes exist singly within the larger cells, but more 

 frequently are multiple, were termed by Henle, and formerly by Kblliker 

 himself, cellules, and the enclosing cell was termed the parent cell. But 

 Kolliker now regards the enclosed vesicles as nuclei, each of which has 

 generally, he says, one or two nucleoli. The spermatic filaments, there- 

 fore, according to Kolliker, are formed within nuclei. 



The appearance of spermatozoids united in fasciculi, which prevails per- 

 haps in all animals, is not owing to their mode of development, but to 

 their tendency, when set free from their formative cellules or nuclei, to 

 arrange themselves thus; a tendency shewing that their bodies attract 

 each other in the same way that blood-disks do in the formation of 

 rouleaux. The fasciculi are formed within the parent cell, when this 

 remains entire after the nuclei or cellules are dissolved; in other cases 

 they are formed in the seminal fluid by the union of spermatozoids which 

 have been wholly set free by the solution of both parent cell and nuclei. 



6. The opinion that the spermatozoids are not independent living 

 animals, but merely elementary parts of the organism in which they exist, 

 is becoming generally adopted. Kolliker, Henle, and apparently Wagner, 

 also, as well as Dujardin, take this side of the question. 



Besides the arguments adduced by Professor Miiller* in support of 

 this opinion, Kolliker urges the narrow limits within which their varieties 

 of form are comprised, a circumstance distinguishing them from En- 

 tozoa, and the character of their movements ; \ but lays especial stress on 

 the fact that they are normal and essential constituents of the seminal 

 fluid. " It cannot be conceived," he says, " that a fluid so important and 

 so strictly vital, in the sense that the blood is vital, which conveys the 

 physical, and even the mental properties of the animal, should be the 

 nidus for the development of foreign and independent beings, whether 

 produced from germs introduced from without, or the result of equivocal 

 generation ; and should afford nourishment to these foreign beings while 

 it still retains its own high endowments. And it is still less conceivable 

 that these independent creatures should be the normal, and, indeed, essential 

 parts of such a fluid." 



We have already seen that the argument in favour of the spermatozoids. 

 being independent animals, drawn from the action of narcotics on them, 

 is not well-founded. 



Supposing them to be merely elementary particles of the organism in 

 which they exist, their movements must be ascribed to a cause analogous 

 to those which produce the vibrations of cilia, and the peculiar movements- 

 of the sensitive plant. 



* Physiology, p. 1477. t See ante p. 40. 



