300 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
the four smaller cells of the 8-cell stage give rise to ectoderm only, while 
the four larger cells produce both endoderm and ectoderm. “ On the 
contrary, neither the four smaller cells nor the four larger ones produce 
ectoderm, exclusively, but it is the four larger, not the four smaller ones, 
which give rise to the greater portion, perhaps all, of the ectoderm.” 
The author cannot at present assent to the statement that the separa- 
tion of the germ-layers is complete at the 44- cell stage. In Giona, from 
the sixth to the eighth generations at least, cell-multiplication is more 
rapid in the anterior and lateral portions of the egg, and this is im- 
portant in determining the shape and position of the blastopore. The 
point where the polar globules form becomes later the centre of the 
dorsal or endodermic half of the egg. In a postscript, the author notes 
a certain amount of corroboration in a recent research by Samassa, 
received after his own was printed. Samassa and Castle are agreed, at 
any rate, that Yan Beneden, Julin, and Seeliger were wrong. 
Formation of Follicular Investments in Ascidians.* — Herr M. 
Floderus has investigated this subject in fourteen simple Ascidians by 
the method of serial sections. His paper contains also a historical 
survey and a copious bibliography. The most important of his results 
are the following. The common rudiment of ovary and testis is a syn- 
cytium, apparently of mesenchymatic origin, which soon becomes hollow. 
At this stage its outer wall is only one cell thick, but the inner consists 
of many layers. This rudiment divides into two parts — an outer, the 
future ovary, and an inner, the future testis. The cells of the ovary, 
originally all similar, divide into the germinal epithelium and the 
primary follicle-cells. After being freed into the cavity of the ovary, 
the ova become surrounded by the follicle cells, which are at first few in 
number. Later they greatly increase in number, and split off, on their 
inner sides a structureless chorion, on their outer sides a similar outer 
follicular membrane; at a slightly later stage they give off numerous 
radial membranes. During a period preceding the formation of yolk- 
spherules in the plasma of the egg, more or less numerous chromatin 
bodies can be observed in it. They seem to arise from a “ Neben- 
nucleolus ” in the germinal vesicle, which passes out through the nuclear 
membrane into the plasma. It is the presence of these bodies which has 
led authors to believe that the follicle- cells arise from the ovum, but the 
egg is already surrounded by the follicle cells before they appear. The 
so-called testa-cells arise from the primary follicular epithelium, but 
are pushed inwards and form a complete envelope, converting the mother 
layer into a secondary follicular epithelium. This secondary epithelium 
again divides into two layers which form the outer and inner follicular 
epithelia. 
New Appendicularise.j' — Dr. H. Lohmann describes three new 
species collected by Vanhoffen on Drygalski’s expedition to Greenland. 
The new forms are named Oikopleura labradoriensis, Oik. vanhoffeni , and 
Fritillaria borealis. 
The author also discusses the formation of the “house.” The 
fibrillar mass and its membranes, as well as the intermediate layers and 
* Zeitschr. f. wiss. Zool., lxi. (1896) pp. 1 63-260 (1 pi.). 
t Bibliotheca Zoologica (Leuckart and Chun), Heft 20 (1896) pp. 25-44 (1 ph). 
