236 Miscellaneous. 



the ventral folds of the last two thoracic segmenti, and of certain 

 segments of the abdomen in the female, and by the separation of the 

 segments of the pleon in the male, Pcdegyge Borrei closely ap- 

 proaches the genus Gj/ge ; but it differs therefrom in that the pleal 

 plates (branchiae of the older authors) instead of being simple are 

 double (b and c), as is the case only in the young females in Gyge 

 hrancluaUs. The ventral fringes exist only on the last two seg- 

 ments of the thorax and on the fii'st segment of the abdomen. In 

 the male we find traces of pleopoda only on the first three abdo- 

 minal segments. In the alcohol which contained the infested 

 Palsemons we obtained a male Cryptoniscian which we find it at 

 present impossible to appropriate to one of the genera examined 

 rather than to the other. 



It is interesting to find that the archaic types of Epicarides, Pro- 

 hopyrus and Palegyge, occur upon genera of Pahiemons inhabiting 

 fresh water. It is true that Palcemonetes vulgaris, the host of Pro- 

 hopyrus pala>monetieola, is a littoral species. But most of ihePalcv- 

 monetes, and especially the common P. varians, live in fresh or 

 brackish waters. This is the case also with the section Macrohra- 

 chium, Sp. Bate, to which Palcemon ornatus and P. dispar belong. 

 The typical Bopyri seem to live exclusively upon the Palsemons of 

 the section Leander, Desm., as defined by Stimpson. Of this abso- 

 lutely marine group most of our European species, P. serratus, P. 

 sqtiiUa, P. rectirostris, &c., form part, each of which bears a parasite 

 of the genus Bopyrus proper. 



We know nothing of the embryogeny of the Macrobraclda, but 

 the arrangement of the lateral spines of the carapace in these Palae- 

 mons presents a character which is only transitory in Leander. 

 The development of Palcemonetes varians, Avhich has been admirably 

 elucidated by P. Mayer, shows us that in these Crustaceans the 

 abdominal feet originate from before backwards, as in the ancestors 

 of the Carides, and not by an abridged process, as in the Leanders. 

 Although from this point of view, as with regard to ethology, Palce- 

 monetes vulgaris forms the passage to the marine Palaemons, we 

 think that it is desirable to attribute to this character a greater 

 phylogenetic importance than that of the absence of the mandibular 

 palpus, upon which P. Mayer relies in deriving the Palcemonetes 

 from Palsemon. 



We therefore regard the Pcdcemonetes and the MacrohracMa as 

 more ancient forms than the Lcandri, forms which have maintained 

 themselves, thanks to their freshwater habitat. The existence upon 

 these ancestral types of archaic genera of Epicarides (Probopyrus 

 and Palegyge) is, we think, a fresh confirmation of the law of paral- 

 lelism between the phylum of the parasites and that of their hosts. 

 — Comptes Rendus, January 23, 1888, p. 304. 



