428 Dr. G. Meissner on the Genus Mermis. ^ '^ »'iG^ 



results confirm the doctrines of KoUiker, Wagner, and ourselves ; 

 that is_, there are parent sperm-cells in which are formed daughter- 

 cells ; in each of these last there is formed a spermatic particle. 

 But Meissner is undecided whether this formation occurs through 

 a metamorphosis of the nucleus of the daughter-cell. Our own 

 observations have led us fully to think that this nucleus is thus 

 metamorphosed. 



The development of the egg is very remarkable, as it shows, 

 what we have never clearly understood before, viz. how botryoidal 

 ovular masses are formed, and moreover carries out the beautiful 

 analogy existing, even to minute details, between the functions of 

 the parent sperm-cell and the ovular cell. An ovular or egg-cell 

 from the ovary is seen ; it increases in size and its nucleus seg- 

 mentates, several nuclei being formed. These nuclei approach 

 the surface of what we will now call the parent egg-cell; diver- 

 ticula are given off from the cell-wall by protrusions containing 

 each a nucleus. These protrusions become constricted and at 

 last appear as little daughter- cells, on the surface of the parent- 

 cell. They now increase at the expense of this last, become 

 pedunculated, and finally appear as larger pedunculated cells 

 attached around a common, insignificant centre. These are the 

 ova, and form groups of variable number — Meissner having ob- 

 served as many as twenty, though there are generally less. Thus 

 formed, their peduncles break ofi^, and they pass from the ovary 

 proper into the other sections of the genital tube. 



There is one other point taken up in connection with this subject 

 by Meissner, to which we shall briefly allude. We refer to the 

 wonderful micropyle of Keber, by which it is alleged that the 

 spermatic particles penetrate the interior of the egg and impreg- 

 nate it. Meissner has seen nothing to justify the view that such 

 a structure exists in the eggs of Mermis excepting the remains of 

 the peduncle above mentioned, and he is not sure of this being 

 hollow. Moreover even if it were hollow, it appears to us wholly 

 dificrent from the special structure insisted upon by Keber. 



As to the embryonic development oi Mermis, our author found 

 nothing essentially different from what had been described by 

 previous observers upon this order (Grube, Leidy, &c.). No 

 proper metamorphosis appears to occur, and therefore the newly- 

 hatched embryos more or less closely resemble in form, &c., the 

 adults. 



In conclusion, we repeat what we said in the beginning, that 

 this memoir is one of the most excellent of its kind we have ever 

 seen, and the care, patience and fidelity displayed therein will 

 ensure attention towards its author as one from whom much may 

 be expected. 



