210 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
layers in siliceous sponges as an “ epibolic pseudogastrulation,” and the 
immigration of flagellate cells, subsequent to settling down, as represent- 
ing the true gastrulation. His memoir is one which none interested in 
embryology can afford to overlook. 
Systematic Position of Placospongia.* — Prof. B. von Lendenfeld 
finds that the resemblance between the Geodm-sterraster and the Placo- 
spowpia-sterraster, on account of which Sollas ranked Placospongia among 
the Tetractinellids, is superficial. The sterrasters differ both in structure 
and development. It seems, therefore, that Keller is right in referring 
the genus to the Monactinellida, and placing it near the Spirastrellidse. 
Protozoa. 
Studies on Protozoa.j — Dr. F. Blochmann brings together a number 
of short notes on Protozoa. The first concern Pelomyxa. On the surface 
of this well-known Ehizopod he observed, on living and preserved 
specimens, numerous fine threads, 10-15 /x in length, not unlike attached 
bacteria, but longer and finer. Observing the median forward streaming 
of the plasm, and the external current of water (as marked by suspended 
carmine), Blochmann observed that the threads also moved forward at 
the same rate, apparently borne by the streaming of a very fine hyaline 
cortical layer. This observation also corroborates an a priori conclusion 
of Biitschli’s. 
Every day for about a week, the author noticed that 60-80 specimens 
of Pelomyxa crept during the night from their shelter in the mud up 
the glass sides of the aquarium, and retired again when the daylight 
became intense. The daily journey was about 20 cm. It is likely that 
putrefaction in the mud drove them out, as it is certain that the light 
drove them back. When twigs of Elodea were placed in the water, and 
made the aquarium more wholesome, the migrations ceased. Besides 
P. villosa , P. viridis , and P. palustris , Blochmann recognizes a fourth 
species which he calls P. Greeffi. He has also an interesting note on 
the way in which Amoeba proteus catches the lively Cyclidium glaucoma , 
often at the rate of 3-5 in 10-15 minutes ! 
The author then notes the occurrence of karyokinesis in Polytoma 
uvella and Monas vivipara ; and describes a new heterotrichous Infusorian 
( Csenomorphina Henrici g. et sp. n.), nearly allied to Csenomorpha, in 
which he was able very clearly to observe the contractile vacuole 
emptying itself externally at the hind end of the cell, where a de- 
pression seemed also to serve at once as an anus and as the canal of the 
vacuole. 
Microscopic Vivisection.^ — Dr. A. Gruber has published under this 
title an interesting popular lecture in which he describes the division 
and conjugation of Stentor coeruleus and its behaviour when cut into 
pieces. A portion of the necklace-like nucleus is essential if a frag- 
ment is to regenerate the whole ; it is the nucleus which gives the cell 
its “ physiognomy ” ; but the behaviour of a fragment shows that each 
particle of protoplasm has “ its own independent Psyche,” and that the 
* Biol. Centralbl., xiv. (1894) pp. 115-6. t Tom. cit., pp. 82-91 (3 pis.). 
X Ber. Nat. Ges. Freiburg, vii. (1893) pp. 47-67 (13 figs.). 
