ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 547 



fugal movement of the germinal vesicle, and terminates with the penetra- 

 tion of the spermatic body. As soon as all the elements of saturation 

 are present, external manifestations of centripetal attraction cease, and 

 there remains only the work of internal equilibration, which ends with 

 the centripetal march of the pronuclei. 



From this point of view it is idle to talk about mechanical con- 

 trivances for preventing the admission of supernumerary spermatozoa, 

 as if the receptivity of the ovum were not self-regulating. The idea 

 that the spermatozoon remains passive until after the extrusion of the 

 polar globules seems to be quite erroneous. 



In the copulation of the sexual cells, the most interesting point is 

 that attraction between the ooplasm and the spermatozoon can manifest 

 itself at a distance. This fact is, however, not quite unique, for some- 

 thing analogous is seen in the attraction between the pronuclei. There 

 are, it seems, two distinct kinds of attraction ; there is that of one 

 nuclear body upon another, which may be called nuclear attraction, and 

 the action of nuclear bodies on the ooplasm which manifests itself in 

 astral lines, and which may be called centripetal attraction. The at- 

 traction of the egg for the spermatozoon is probably polar, and the place 

 of penetration a predetermined point or region. On this point, however, 

 the evidence is very conflicting ; the most important memoir on this 

 point is that of Kupfier and Benecke on the fertilization of the egg of 

 the lamprey. The important points in this and in other essays are 

 indicated by Dr. Whitman. 



Human Ovum.* — Dr. W. Nagel gives a full account of his observa- 

 tions on that rare subject of satisfactory investigation — the human ovum. 

 The principal results have been already noticed. "j" 



The first part of the lengthy paper is taken up with historical 

 reference to previous observations, of which a full bibliography is 

 appended. After describing his material and mode of investigation, the 

 author discusses and figures the primordial ovum and primary follicle, 

 the subsequent growth of both of these, and the conditions observable in 

 maturity. In the latter, he describes (1) the epithelium of the oviun ; 

 (2) the zona pellucida ; (3) a perivitelline space ; (4) a narrow, clear 

 cortical zone of the vitellus ; (5) a broader, finely granular, protoplasmic 

 zone ; (6) a central deutoplasmic zone ; (7) the germinal vesicle and 

 spot. The ovary of a newly born child and that of an ape (Macacus) are 

 described, and many relevant questions are incidentally discussed. 



Spermatogenesis of Mammals4 — Prof. V. v. Ebner communicates an 

 important memoir on the spermatogenesis of mammals, in which he 

 resumes the investigation which he busied himself with seventeen years 

 ago. He discusses in the first two chapters the nomenclature employed 

 by investigators, the material and method of investigation, and the actual 

 state of the question. In a third chapter he investigates the relation of 

 the basal nuclei of the spermatoblasts to the cells of Sertoli and the 

 spermatogonia of v. La Valette St. George. Fourthly he shows in what 

 cells within the testicular canals division is really to be observed. Then 

 he discusses the granular excretions of the spermatoblasts, the absorption 

 of the fat by Sertoli's cells, and the general physiology of the spermato- 

 blasts. The last chapter is occupied with a description of the topo- 



* Arch. f. Mikr. Anat., xxxi. (1888) pp. 342-423 (2 pis.). 



t See this Journal, 1887, p. 932. J Tom. cit., pp. 236-92 (3 pis.). 



