258 BOPYRID.E. 



seven segments of the body is furnished with a pair of legs, 

 affixed within the lateral margin on the underside; they 

 are more elongated than in the Bopyri, and more or less 

 hooked for prehension ; the'y are nearly uniform in size, 

 the anterior pair being, however, the strongest, and the 

 posterior the longest and most slender in one or more of 

 the species.* 



Each of the segments of the tail is furnished on the 

 underside with a pair of branchial appendages differing 

 in form in the different species, but very strongly fringed 

 with long setae. 



The female is a large inert mass of animal matter, 

 destitute of appendages, and is affixed to the animal on 

 which it is parasitic. Tt is divided into two portions, the 

 one consisting, according to Lilljeborg, of four distinct 

 segments, which supports the organ or tube by which it 

 adheres to its prey, whilst the hind part of the body 

 consists of a simple sac for holding the eggs. 



Writing to us on this genus, Dr. Fritz Miiller says, 

 " Changes in form not less important than those observed 

 in the Hyperina are to be seen also in the Bopyridae. I 

 have already published the description of a new genus 

 of this family, Entoniscus, whose retrograde metamor- 

 phosis proceeds much farther than that of Bopyrus (see 

 p. 265 post, note f). I have since found another species 

 of the same genus living in different Brachyura (Xantho, 

 &c.), and a second genus (Cryptoniscus, F. Miiller, 

 MSS.), almost unrecognizable when adult ; indeed the 

 female of it then resembles Planaria lactea rather than 

 an Isopod. It is, moreover, very interesting in its habits ; 

 it does not take its sustenance directly from the little 

 Pagurus, on whom it is fixed, but from the roots of the 



* In the species observed by Lilljeborg and Fritz Miiller (Entoniscus 

 Galathece) the young have only six pairs of legs. 



