1694] Embryology. 439 
EMBRYOLOGY. 
Development of Sponges.’—Otto Wass in a comprehensive 
paper describes the egg development and metamorphosis of several 
representatives of the Cornacuspongiae, including under this head the 
Monaxonida, with the exception of the Clavulina and the horny spon- 
ges. For the Monaxonida the embryonic development of Myxilla and 
Chalinula, and the metamorphosis of Axinella and Gellius, are describ- 
edin detail. For the horny sponges, the development of Euspongia. 
and Hircinia is outlined. In addition, there are scattered observations 
on many other Naples cornacuspongiae, and lastly the author presents 
the results of a renewed study of Spongilla. 
A fundamental uniformity both as regards embryonic development 
and metamorphosis, was found to prevail throughout these sponges. 
The account of the metamorphosis differs but little from the author’s 
previous account of the metamorphosis of the Esperia larva, and is 
very similar to that given by Yves Delage in his last paper (reviewed 
in the January NATURALIST). 
In the marine monaxonida described, the segmentation is unequal. 
Micromeres in an epibolic fashion surround a mass of macromeres, 
except at the posterior pole. The micromeres become the ciliated epi- 
thelium of the larva, the macromeres constitute the inner mass. e 
a thus consists of two layers. In the inner mass some of the cells 
remain undifferentiated, while the rest alter both in nucleus and cell 
body, and are collectively known as differentiated cells. Certain of 
these differentiated cells arrange themselves in an epithelial manner at 
the surface of the posterior pole. The undifferentiated cells of the 
inner mass become the amoeboid cells of the adult, from which the 
reproductive elements aredeveloped. Thus the division into germ and 
Somatic cells is very early brought about. 
_ In the horny sponges the segmentation does not lead to a true moru- 
la which dilaminates into an outer layer and an inner mass, a8 Schulze 
thought. The segmentation here too is unequal, and the micromeres 
surround the macromeres as in the monaxonida, the former becoming 
‘Edited by E. A. Andrews, Baltimore Md., to whom communications may be 
addressed, 
Dag Embryonal Entwicklung und Metamorphose der Cornacuspongien, von Dr. 
Wass, Zoologische Jahrbücher. Abth. für Anat. und Ontogenie. Bd. VII, 2 
Hit, 1893 
. 
