44 



and is certainly owing to the fact that the membrane surrounding the ovisac was not 

 sufficiently stifl'ened, when — or shortly after — the ovisac was laid. In Mysidion and 

 Aspidoecia all ovisacs, from the moment they are laid till the larvae have swum out, are 

 hinged to the lips of the genital apertures by stalks, which are rather short (in Mysidion), 

 or very short (in Aspidoecia), so that we see pretty frequently six to seven, or sometimes 

 more ovisacs hinged at one genital aperture (pi. XI, fig. 3 b); fig. 2 b in pi. XII shows 

 how the lips of the genital aperture and the part behind them are covered by a plate formed 

 of a coagulated viscous substance, from which the stalks of the ovisacs proceed; the plate 

 must be considered as the coalescent basal parts of the stalks. 



The genus Stenothocheres deviates considerably from the other genera, but unfor- 

 tunately I am not prepared to represent its conditions as precisely as I should like to do. 

 Of one of its two species I have seen but one single female with eggs, of the other (St. 

 egregius) my material is indeed very abundant, but not particularly good, some of it being 

 very old, and most of it, though of later date, having shrunk somewhat, because its hosts 

 — while still alive — had been put into too strong spirit. In many cases I only found a 

 single lump of eggs, which was rather larger, or considerably larger than the female, had 

 no regular form, and was not surrounded by a common membrane. Sometimes, but not 

 always, this lump seems to consist of two — seldom three — smaller coalescent lumps; 

 four instances were of a more instructive nature. A female of St. Sarsii showed two lumps 

 of about equal size, one of which was free, the other (no doubt accidentally) adhering to the 

 female. One of them is illustrated in pi. I, fig. 2 c, which shows the irregular shape and 

 want of a common membrane, as well as the size in proportion to the largest female which 

 is illustrated in fig. 2 a and magnified to the same scale. The three other cases have been 

 observed in St. egregius; in all of them the female had doubtless finished laying eggs. In 

 one case two smaller, short oval lumps were glued together at their extremities, one con- 

 taining seven, the other nine eggs; in the second there were two lumps, one of them a 

 little larger, the other a little smaller than the female; in the third case there was an 

 oblong lump containing ten eggs, the young animals of which were a little more than half- 

 developed, six to seven larvae winch were about to break out of the shells, and thirteen 

 free larvae; all this indicated that the eggs had been laid at intervals. It seems probable, 

 on the whole, that the eggs are not laid all at the same time, but successively, though the 

 intervals must be rather short, whereas the ovisacs, at least in most and probably in 

 all the other genera, are deposed at rather considerable intervals; this is easily seen from 

 the fact that among ovisacs deposed by the same female, we often find one or two which 

 have evidently been laid recently, whereas some others contain more or less developed larvae. 

 We sum up our observations in the following statement, that in Stenothocheres the eggs are 

 deposed in one single large and free lump, or in a couple of smaller and free lumps of 

 irregular form and without the common membrane which belongs to a proper ovisac; and 

 finally, it seems rather probable that the eggs are not laid all at the same time. 



