43 



the proximal part longer than the distal one, the former ending- in a thick, bell-shaped and 

 thick-skinned, hairy expansion (pi. II, fig. 4 b); 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 

 glued 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. 



c. 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 Sphceronella they are unknown to me. In the two species of the genus 

 Stenothocheres they differ 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 Momoeoscelis, Sphceronella, 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-globnlar, 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 Sphceronella 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 Sphcer. 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 tiling, 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 Homoeoscelis, Sphceronella 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* 



