ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
517 
oils to speak of the persistence of the nuclear ribbon as such, or to 
maintain that it forms the figures. 
Superfluous products resulting from the successive dissolutions pass 
out into the cytoplasm and serve to nourish it, forming vitelline plates. 
There are no longitudinal nor transverse divisions of the nuclein 
elements at any stage in the whole process. At the time of the polar 
kineses, some of the products of the nucleolar dissolution which is in 
process form the rods of the figures, but it is nonsense to say that these 
come directly from the primitive ribbon. The authors offer severe 
criticism of the results reached by other observers, whose vision, they 
say, has been distorted by theoretical prejudice. 
Segmentation of Ovum in Sheep.* — Mr. R. Assheton has succeeded 
in obtaining a very fairly perfect series of specimens from the time 
of fertilisation to shortly before the stage at which Bonnet’s account 
begins. His results agree with wbat he has already observed in the 
pig. At an early stage, perhaps as early as the 8-segment stage, the 
future epiblast and hypoblast are differentiated. The hypoblast sur- 
rounds the epiblast , so that at the morula stage the embryo consists of 
a few internal epiblast cells surrounded by hypoblast cells, which at 
one pole form a thicker investment than elsewhere. In the middle of 
this thickened mass of hypoblast the cavity of the blastodermic vesicle 
arises. Subsequently, by the rupture of the hypoblast, the epiblast 
comes to the surface. The cavity of the blastocyst is not the segmenta- 
tion-cavity, but (as Robinson stated) the archenteron surrounded on all 
sides by hypoblast. Thus there is no blastopore. The hypoblast is, 
owing to mechanical and physical causes, double over part of the wall. 
Assheton goes on to consider the hypothesis of the hypoblastic origin 
of the trophoblast. 
Spermatogenesis in Man.f— Prof. K. von Bardeleben makes his 
eighth contribution on this subject. (1) He gives further proof that 
the intermediate-cells ( Zwischenzellen ) pass through the walls of the 
seminal tubules into the lumen, bearing crystals, pigment, and fat with 
them. (2) The development of the spermatides into the “spermato- 
somes” or unripe spermatozoa is then discussed, seven stages being 
described. There is what may be called a futile attempt at continued 
cell-division — a “ kytokinesis” without karyokinesis — and there is an 
adaptation of external form in relation to movement. (3) The occur- 
rence of an accessory form (Nebenform) of spermatosome and spermato- 
zoon, in addition to the main form (j Eauptforni), is upheld. 
Rudimentary Ova in Frog’s Testis.:*: — Herr F. Friedmann describes 
a case in which distinct ova occurred in the seminiferous tubules of 
liana viridis. The ova showed none of the typical yolk-plates, nor any 
of the characteristic brownish pigment, but were otherwise clearly 
ova. Fifteen were fairly well developed ; three were degenerate and 
like the cells in Bidder’s organ. 
Effect of Mechanical Stimulus on Unfertilised Ova of Silkmoth.§ 
— J. Perez notes that friction, washing with sulphuric acid, and other 
* Quart. Journ. Micr. Sci., xli. (1898) pp. 205-62 (4 pis. and 6 figs.). 
t Jenaische Zeitschr. f. Naturvviss., xxxi. (1898) pp. 475-520 (3 pis. ancl 5 figs.). 
X Arch. Mikr. Anat., lii. (1898) pp. 248-62 (1 pi.). 
§ Proces Verb. Soc. Sci. Bordeaux, 1896-7 (received 1898), pp. 9-10. 
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