624 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Forifera. 
Anatomy of Leucosolenia clathrus.* — Mr. E. A. Minchin has been 
able to discover the oscula in this sponge, from which they have hitherto 
been supposed to be absent. He finds, indeed, that the oscula are very 
large and distinct, though they are provided with a sphincter by which 
they can, for a time, be completely closed. This sphincter consists of 
two layers of ectoderm, with a few scattered amoeboid cells between ; 
the contractile cells are the ectodermal epithelium. In connection with 
this point reference is made to the division by von Lendenfeld of the 
Coelenterata into Mesodermalia (Sponges) and Epithelaria (other Coel- 
enterata), and it is pointed out that the only chief organs of the sponge 
which can certainly be said to be of mesodermal origin are the connective 
tissue system and the generative elements. The author gives a graphic 
explanation of the cause of the general error as to the absence of oscula, 
and shows that Haeckel’s four varieties of this sponge are only different 
states of contraction ; they are no more zoological varieties than a polyp 
with contracted tentacles is a variety of a polyp with expanded tentacles. 
The endoderm has been described as multilarainate, but this is merely 
temporary, and is a mechanical result of the contraction of the whole 
sponge. 
Development of Gemmules in Ephydatia fluviatilis.f — Mr. W. 
Zykoff is, in opposition to Goette, strongly of opinion that neither the 
canals nor the flagellated chambers take any part in the formation of 
the gemmules of this freshwater Sponge. As the yolk-substance becomes 
massed up and continues to increase the future gemmule may be seen 
dividing into two parts — the central mass which consists of yolk-cells 
with amoeboid cells of the mesenchym scattered here and there amongst 
them, and the peripheral layer which consists of several rows of mesen- 
chym cells and gradually passes into the surrounding tissue of the 
mesenchym. The further development of the gemmule consists in the 
peripheral cells taking on a club-shaped form, when their thickened 
ends with the nuclei are directed outwards, the median part thins out, 
and the inner end is flattened out ; these cells are arranged radially in 
one layer, and not in two or three, as Goette supposes. In consequence 
of this arrangement they form a continuous layer on the spherical 
surface of the central mass of the future gemmule. Later on, the 
amphidiscs appear between the club-shaped cells of the envelope; the 
author w r as unable to detect the silicoblasts figured by Lieberkiihn. 
The formation of the gemmule is completed by the development of two 
chitinous cuticles; and after this the club-shaped cells lose their 
definite form and are gradually absorbed. 
Protozoa. 
Argentine Protozoa.;]; — Prof. J. Frenzel describes Guttulidium 
tinctum g. et sp. n., a sluggish naked amoeba with hardly more than a 
suggestion of pseudopodia, and with a compact, angled nucleus ; 
* Quart. Journ. Micr. Sci., xxxiii. (1892) pp. 477-95 (1 pi.). 
t Bull. Soc. Imp. St. Petersburg, 1892, pp. 1-16 (2 pis.). 
X Bibliotheca Zool., Heft 12 (1892) pp. 50 (6 pis., not published). 
