148 
The testes (fig. 1, 13) are ovoid bodies with a length of 0,5 mm and 
a diameter of 0,35 mm which lie one behind the other in the hinder half 
of the body. The ovary and receptaculum seminis are ovoid bodies of 
‘about the same size, the former of which lies directly in front of the 
latter (fig. 1, 9 and 10) and the dimensions of which are about 0,35 mm 
by 0,3 mm: they lie towards the left side of the body and near its 
middle. The oviduct (fig. 5, 3) proceeds from the right side of the ovary 
(fig. 5, 1) and, running a short distance to the right, meets the recepta- 
culum seminis (fig. 5, 2) and the Laurer’s canal (fig. 5, 4) at the same 
place. The latter canal is rather long, extending dorsally and posteri- 
orly, and finally opens to the outside in the dorsal body-wall above the 
receptaculum seminis. The oviduct, after receiving these two ducts, 
bends directly ventrally and after being joined by the median yolk-duct 
(fig. 5, 5) expands to form the ootype (fig. 5, 6). The uterus (fig. 5, 7) 
proceeds from the ventral portion of the ootype and bends at once on 
itself and runs dorsally: it is very long extending to the hinder end of 
the body. The average size of the egg is 0,024 mm by 0,014mm. Sur- 
rounding the ootype are the elongated so-called shell-glands (fig. 5, 8). 
The yolk-glands (fig. 1, 12) extend from the region of the ovary to the 
hinder end of the body. They are grouped in a series of indistinct fol- 
licles, each follicle consisting of strings of small glands arranged in 
date lines from a common point. 
In conclusion I wish to thank Hofrat Professor Dr. L. von Graff 
most heartly for the privilege of working in his laboratory during the 
Winter and him and all of my colleagues in the Zoological Institute in 
Graz for their many kindnesses to me. 
Graz, April, 1911. 
5. Über den Ursprung der Microsclere der Desmacidoniden. 
Von Dr. Ernst Hentschel, Hamburg. 
eingeg. 28. April 1911. 
Die merkwürdigen, meist sehr kleinen Skeletkörper der Kiesel- 
schwämme, welche man als Microsclere bezeichnet, haben um ihrer auf- 
fallenden, oft überaus komplizierten Gestalt willen mehrfach zu Ver- 
suchen angeregt, diese Gestalt zu erklären. Es ist bemerkenswert, wie 
wenig dabei die organische Zweckmäßigkeit, die sonst so häufig heran- 
gezogen wird, als Faktor der Gestaltung angenommen worden ist, Die 
meist mehr oder weniger regellose Lage der Microsclere im Schwamm- 
körper ließ nur selten eine Beziehung zu den Lebensfunktionen annehm- 
bar erscheinen, und vor allem keine Beziehung, welche so kompliziert 
gestaltete Gebilde notwendig machen würde. Vorwiegend sind physi- 
