ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 343 
striation or pores. On an ovum of 94 p there was a distinct micropyle 
near the nucleus. There is no circumvitelliue space. The cell consists 
at first of protoplasm alone, but afterwards of deutoplasm also. With 
growtli the form changes from round to oval, and chromatin fragments 
pass from the nucleus into the cell-substance. The nucleus, at first 
round and central, becomes slightly oval and ex-centric ; the part at 
which the nucleolus lies is always nearest the surface of the ovum. 
The nuclear membrane, at first slightly undulating, becomes quite 
smooth. With the passage of chromatin fragments from the nucleus to 
the cell-substance the nuclear framework gradually disappears, but the 
nucleolus — “ the most essential part ” — persists, though changed during 
maturation into a clump of chromatin spheres. 
“ Oolysis ” in Seps.* — Dr. P. Mingazzini describes the complex 
destruction of ova — i. e. the “ oolysis ” — which occurs in the ovary of 
Seps ehalcides. Only a small percentage of the large number of ova 
produced are utilized, and phenomena of degeneration occur comparable 
to those which Sanfelice has described in the testis. Apart from the 
ovarian degeneration, there is also a destruction of embryos at various 
grades of development ; this does not seem to be injurious to adjacent 
ova, which undergo normal development. 
Fertilization of Ovum of Slow-worm.+ — Dr. A. Oppel has observed 
in the fertilized ova of Angnis fragilis, the formation of a male and a 
female pronucleus, and their gradual approach to one another. Besides 
the male prouucleus there were usually numerous accessory sperm- 
nuclei of unknown significance. The male pronucleus exhibits a proto- 
plasmic field with radiations. The structure formed in conjugation 
exhibits a regular division-figure, whose axis is approximately parallel 
to the surface of the blastoderm. From this division arise the two first 
segmentation-nuclei. The accessory sperm-nuclei play no part in the 
conjugation of nuclei ; they undergo several divisions and then abort. 
The protoplasmic field of the sperm-nucleus is formed under the 
influence of this element, and the radiations from it exteud through the 
blastoderm to the surface. 
Gelatinous Sheath round Frog Ova.J — Dr. H. Bernard and Herr 
K. Bratuscheck have discovered a new utility in the spheres of frog 
spawn jelly. It has been pointed out by various naturalists that this 
sheath protects the ova from drought, pressure, birds (except ducks), 
fishes, water-snails, &c. The authors also show that Gammarus pulex 
seems to have a great repugnance to the slime, and also to the young 
tadpoles, perhaps on account of some bad taste. The spheres also 
preserve interspaces between the crowded eggs, and in these there are 
usually nests of green sw’arm-spores, which must likewise be advantage- 
ous. And is it not the case that the gelatinous envelope is of some 
moment in connection with the penetration of spermatozoa ? 
But what the authors have shown is this: — The envelope aids the 
pigment of the ova in utilizing the heat of the sun’s rays, allowing these 
to pass through, but retaining those of longer wave length, which radiate 
* Atti R. Aocad. Lincei, ser. v.. i (1892) pp. 41-5. 
t Arch. f. Mikr. Anut., xxxix. (1892) pp. 215-90 (4 pis). 
X Biol. Centralbl., xi. (IsOl) pp. 691-4. 
