190 SUMMAEY OF CURRENT RESEARCHES RELATING TO 



membrane is formed round tLe entire egg, and the main mass of the 

 pole-plasma surrounds itself internally with an undulating membrane 

 at the contact surface with the yolk. Within the pole-plasma one then 

 finds the spermatozoon and the provisional female pronucleus. Their 

 position is not fixed, for the plasma is very mobile. Some time after the 

 retraction of the axial strand the apical knob is raised towards the watch- 

 glass-like arch, comes in contact with its inner surface, receives particles 

 from the already-mentioned imprisoned or impeded spermatozoa, and is 

 retracted into the main mass. The second polar body is formed ; the 

 fi.nal female pronucleus remains ; and the sperm takes up a definite 

 position in relation to it. 



A quarter of an hour after fertilization both elements begin to change. 

 The female pronucleus becomes pale, diffuse, and rather larger. The 

 sperm-head breaks up into spherical, connected, linearly disposed ele- 

 ments. The formation of an associated " sun-figure " is described. The 

 " spermatomerites " come into contact with the female nucleus, which 

 takes or has taken the form of a group of spherical " ovomerites." The 

 two sets of elements come into intimate contact, undergo binary division 

 into smaller and smaller portions, but do not fuse. Each merite consists 

 of a body and one or two granules or microsomata. At the end of the 

 third hour the bodies of the merites fuse, the segmentation nucleus is 

 formed, and the undulating membrane of the pole-plasma dissolves. 



The microsomata, which become free when the merites fuse, arrange 

 themselves in short chains. They become grouped in an axial plate. 

 The central mass of the sun probably falls into two masses with two 

 suns, disposed at opposite poles in relation to the plate. Spindle strands 

 appear, the short chains of the plate curve into loops, and a metaphasis 

 sets in. After the formation of daughter-nuclei the pole-plasma begins 

 to constrict in the axis of ovum. The author concludes his memoir with 

 a comparison between his results and those of other investigators of 

 fertilization. 



Observations on Human Spermatozoa.* — Mr. E. M. Nelson gives 

 an account of some observations on the human spermatozoon. He thinks 

 that the head or spore, as he calls it, has not been correctly figured 

 hitherto. Its outline is oviform, the part towards the tail being the 

 small end, but in all drawings which he has met with, the reverse of this 

 is represented. The spore fits into a cup, and the edge of this can be 

 distinctly seen both in front and side views, though the outline of the 

 head has always been represented as unbroken. At the bottom of the 

 cup there is what Mr. Nelson calls the calyx ; this is exceedingly 

 variable. Between the cup and the tail proper there is the stem, which 

 varies in thickness ; then there is the break which the author calls the 

 joint ; the tail is fairly constant in thickness and length. On the spore 

 there is a process which it is proposed to call the filament, and not the 

 flagellum (though it is like one), inasmuch as it is regarded as a director, 

 or kind of antenna for the purpose of guiding the spore into an aperture 

 in the ovum. As many as four nuclei have been observed in the spore 

 of a human spermatozoon, but, though Mr. Nelson does not say so, this 

 must be a very abnormal case. 



Epithelial Glands in Batrachian Larvse.f — Prof. F. E. Schulze 

 reports an interesting histological discovery made by him, while ex- 



* Journ. Quek. Mikr. Olub, iii. (1889) pp. 310-4 (1 pi.). 



t Biol. Centralbl., viii. (18S8) pp. 580-2 ; Abh. K. Preuss. Akad. Berlin, 1888, 

 pp. 46-9. 



