36 SPERMATIC PARTICLES. 



investigation, and especially in the department of minute and vital morphology, where 

 the contingencies to error and illusion are more prominent than in grosser studies. 



The grand result at which 1 have arrived in these investigations, and which has an 

 importance sufficient to justify me in the details already given, and those which shall 

 be presented hereafter, may be stated as follows : — 



That, throughout the range of vertebrated animals, the morphological changes in the 

 sperm-cell preceding the formation of the spermatic particles are identical in their charac- 

 ter with the morphological changes in the ovum preceding the formation of the new being. 

 The processes are the vitalization of the sperm-cell in the male, and of the ovum in 

 the female, by the continued segmentation of the nucleus or vitellus, until each is a mul- 

 berry mass. The changes sequent upon this are of several kinds. Two of them, how- 

 ever, may be mentioned as apparently the most important and best known, viz. : — 1st. 

 The liquefaction of the segmented contents into a minute granular blastema, out of 

 which are formed, in the one case, spermatic particles, in the other, a new being ; and 

 2d. The immediate passage of the segmented contents ; in the one case, each cell 

 becoming a spermatic particle, in the other, masses of cells forming the organs of the 

 embryo. 



There appear to be other modes than these, both with the sperm-cell and the ovum ; 

 but they are very imperfectly understood, and may here be omitted. 



I shall now take up the description of my observations in the four grand classes, 

 commencing with the lowest : — 



1st. Fishes. — The spermatic particles of fishes exist under two forms, and these 

 corresponding to the two forms of their testes of which we have already spoken. 



In the higher osseous fishes, where the structure of the testes is tubular, these bodies 

 consist of a very minute globular or cordate cephalic portion, to which is appended a 

 still more minute tail, the presence of the latter, however, being far from constant in all 

 specimens. 



In the Plagiostomes, where, as we have seen, the structure of the testicle is cellular, 

 and not tubular, the form of these bodies is quite different ; they are of a much larger 

 size, and are long and filiform, their cephalic portion being only thickened, and gradu- 

 ally tapering off into a tail, which, compared with the body, is not very long. The ex- 

 istence of these two forms is important, as we shall soon perceive. 



The formation of the spermatic particles among fishes has, as far as I am aware, 

 been observed only in the Plagiostomes. And with the observations of Hallman* 



* Muller's ArcUv, 1840, p. 467. 



