634 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
one germ-cell and two terminal cells. Some of the author’s results 
distinctly corroborate the theory of Hallez that the Nematode larva is 
referable to the Trochophore type, but he is inclined to suspect that the 
late mesodermic formation of the Nematode anus points to derivation 
from Hatschek’s Protrochula. 
As to the sexual relations of Bradynema , the author comes to the 
interesting conclusion that the male larvae are protandric hermaphro- 
dites, which subsequently become the adult female parasites, and that 
the female larvae have really not to do with the continuance of the 
species. 
Development of Pseudalius inflexns.* — Herr Th. List finds that, in 
this form, the first segmentation-plane of the ovum is not in the middle 
line, so that the blastomeres are of unequal size. The smaller forms 
the ectoderm, the larger the endoderm. In the twelve-cell stage the 
cell-plate is distinctly two-layered, consisting of an eight-celled dorsal 
ectoderm and a four-celled ventral endoderm. As cell-division goes on, 
an amphiblastula is formed with a distinct blastula cavity. The ecto- 
derm cells continue to increase very rapidly, so that the amphiblastula 
becomes a flat two-layered plate which forms a gastrula by epibole. 
The prostoma, which is at first a longitudinal slit, closes from behind 
forwards, leaving for some time a rounded opening at the anterior end. 
Two primitive mesoblasts appear at the sixteen-cell stage, having 
originated from the ectoderm. They give rise to long rows of meso- 
blastic cells which, in cross section, form a ring round the intestine, the 
ventral rows being the latest formed. Later, by the close connection of 
mesoderm and ectoderm cells, a homocoele is formed, which secondarily 
becomes schizocoelic. The nervous system arises, towards the end of 
gastrulation, from the upper thickened region of the ectoderm. The 
mouth and anus are formed as secondary invaginations after the closure 
of the prostoma. 
Trichinosis.f — The occurrence of what appears to be the first case of 
an epidemic of trichinosis in Belgium led Dr. P. Cerfontaine to a 
research on this subject. He finds that, during the first two periods the 
cysts are destroyed in the stomach, in which the larval Trichinae either 
live for some time, or they pass at once into the small intestine. In the 
intestine they grow, and fecundation is effected on and after the second 
day of infection ; the males, after a stay of varying length in the intes- 
tine, are expelled with the faeces. In the female the development of the 
larvae commences immediately after fertilization. The embryos begin to 
be set free about the sixth day of infection. A certain number of the 
females penetrate into the wall of the intestine, and even into the 
mesentery ; these have more chance of infesting the organism than those 
which remain in the intestinal canal, since their embryos cannot be 
expelled with the faeces. It is probably by means of the lymphatic 
systems that the parasites first make their way into the tissues of their 
host. The fact that adult Trichinae penetrate the tissues gives an 
explanation of the violence of the gastro-intestinal troubles which often 
characterize the beginning of the malady. 
* Biol. Centralbl., xiii. (1893) pp. 312-3 (1 fig.). 
t Bull. Acad. Koy. Belg., lxiii. (1893) pp. 461-88 (1 pi.). 
