43 
the proximal part longer than the distal one, the former ending in a thick, bell-shaped and 
thick-skinned, hairy expansion (pl. II, fig. 4b); the distal part comes out of the bell in 
which its extremity forms a little ball; its other extremity expands into a disk which is 
elued on to the Amphipod. I have found several of such threads and examined them as 
carefully as possible, but it is quite incomprehensible to me how the animal has been 
capable of producing them. 
ce. The Ovisacs and the Development of the Eggs. 
1. The Ovisacs. Of forty-one species the ovisacs have been found, and only in 
two species of Spheronella they are wnknown to me. In the two species of the genus 
Stenothocheres they ditfer so much from those met with in the other genera, that I prefer to 
leave out this genus for the present, setting it aside for separate treatment. 
In Homoeoscelis, Spheronella, Choniostoma, Mysidion and Aspidoecia each female 
deposes several — no doubt at least four or five — or many ovisacs, which, if not deformed 
by pressure, are sub-globular, oval or, in Mysidion, of a short pyriform shape. In Homoeo- 
scelis minuta, of which I have examined a large material, I can assert that the female 
deposes at most eight ovisacs, though usually but five to seven are found; in Choniostoma 
the maximum seems to be twelve, in Aspidoecia thirteen to fourteen, in Mysidion seventeen 
or still more. In the numerous species of Spheronella which live in the marsupium of 
Amphipoda, I cannot indicate the maximum of the ovisacs, partly because my material of 
each particular species is too small, or because not unfrequently a couple or more of females 
are lodged in the same marsupium, partly because, in many cases, one cannot be certain 
that some of the sacs have not been washed away. Better information can be given about 
some species living in the marsupium of Isopoda and Cumacea: in Spher. Munnopsidis I 
found one female with twenty ovisacs, in S. decorata the same number, in one specimen 
of S. modesta twenty-two, in another twenty-eight ovisacs, all laid by one single female. 
This latter number may be supposed to be about the maximum, not only in the above- 
mentioned species, but in the whole family. It is very difficult to indicate the smallest 
number of ovisacs made by normal females of the different species, as, for one thing, it has 
to be ascertained, whether the specimen in hand has altogether finished laying eggs, and a 
considerable material has to be examined for this purpose alone; still, though I have not 
done this, I think I can say that the number is never less than four or five, perhaps seldom 
less than five or six. In all five genera each ovisac is smoothly rounded, its eggs being 
as usual enclosed in a common membrane. In Homocoscelis, Spheronella and Choniostoma 
all ovisacs are deposed freely without being attached to the female or having any real 
connection with each other. Indeed, we see rather frequently some, or many, of the 
ovisacs sticking together, or one, or several of them, adhering somewhere to the body 
of the female; however, this kind of adhesion is of a secondary, quite unimportant nature, 
6* 
