22 G. O. Sars. 
contains a strong muscular band passing through it diagon- 
ally. From the place where this muscle terminates, springs 
the sensory bristle of the anterior edge, and immediately 
inside it, a small hook-shaped denticle is seen projecting 
inwards. The outer part of the antennula is rather narrow 
and more or less curved, so as to meet, with its tip, the 
corresponding antennula on the other side, when bent in. 
Each antennula is armed on the obtuseiy rounded end with 
4 strongly curved hooks, between which the usual fascicle 
of olfactory papille may be discerned (see fig. 7). 
The structure of the Ist pair of legs and that of the 
testes seems to agree with that found in M. australiensis 
and tenutcornis. 
In both sexes the body is highly pellucid and almost 
colourless. Only in large female specimens, a more or less 
distinctly rosy tinge may sometimes be observed. The egg 
contained in the ephippium is of a brick-red colour. 
Biological Observations. 
Of this form at first only a comparatively small number 
of female specimens were hatched in some of my aquaria. 
In the course of a few days they reached maturity, and 
began to propagate in the usual parthenogenetical manner, 
several successive generations of this kind being observed, 
whereby the number of specimens increased considerably. 
But at the same time the fertility of the individuals dimi- 
nished conspicuously, and after the lapse of some time, the 
bisexual or gamogenetic period was seen to have set 
in, the greater number of the females now having the 
ovaries filled with a brick-red contents and showing traces of 
the ephippial formation. At this time, male specimens were 
observed in great numbers, eagerly pursuing the females, and 
