216 SUMMARY OF CURRENT RESEARCHES RELATING TO 



«. Crustacea. 



Excretion in Brachyurous Crustacea.* — M. P. Marchal, noting that 

 the excretory system of the Decapoda has hardly heen investigated, 

 exeept in the crayfish, has made an investigation into that of Maia 

 squinado. He finds that the apparatus consists of gland, reservoir, and 

 excretory duct ; the two reservoirs are of enormous size, and occupy the 

 whole of the sternal part of the cephalic region in front of the mouth. 

 Each consists of a vestibule, a proper bladder, and a hind-bladder ; where 

 the two latter unite, the orifice of the gland is hidden under a bridge 

 of tendon ; the excretory duct opens at the antero-external part of the 

 bladder, in a funnel-shaped depression formed by the vestibule. 



The excretory orifice is, during repose of the apparatus, hidden by a 

 calcareous plate ; but when the elevator muscle, which is connected with 

 it contracts, the plate is raised, and the chitinous membranes which are 

 inserted into it are exposed ; the excretory orifice is thus able to evacuate 

 the excreted liquid. A crab under examination was seen to put its 

 tubercles into movement twice in an hour and a half; the tubercle is 

 kept raised for some moments, is then lowered, and moved backwards 

 and forwards several times so as to get rid of the last drops of the fluid. 

 At the same time the palps of the second and third gnathites emerge 

 and set up a very rapid undulating movement, the object of which is, 

 evidently, to drive away the excreted fluid from the mouth and branchial 

 cavity. 



The bladders of either side are not, necessarily, emptied at the same 

 time, and appear to be independent of one another ; the emptying of the 

 bladder is brought about by the action of muscular bundles, and the 

 organ has, possibly, some contractility of its own, while the action of 

 the tubercle appears to have a favourable influence on the emission of 

 the liquid. On the other hand, the oblique course taken by the canal 

 causes the two lips to be applied against one another, and so to close 

 the entrance when the pressure is from the exterior ; the opposite happens 

 when the pressure is from the interior. 



The quantity of fluid excreted is considerable, a single crab of 

 780 grammes weight giving in a few seconds 13 c.cm. and one as much 

 as 17 c.cm.; the liquid is perfectly limpid, with a strong saltish taste, 

 and of a density (with the urinometer) of 1030. 



Green Gland of Crayfish. ] — Herr B. Eawitz answers Prof. Grobben's 

 strictures on his conclusions as to the structure of the green gland of 

 Astacus. He remains of his own opinion, and his response has little 

 more than personal interest. 



The Bopyridse4 — Prof. A. Giard and M. J. Bonnier have published 

 a monograph on the Bopyridfe, various preliminary notices of which 

 have been given in this Journal. In the present memoir the Ionime 

 and Entoniscidse only have been considered ; for each a type has been 

 selected, for the former Cepon elegans, which is parasitic on Pilnmnus 

 hirtellus, and for the latter Entoniscus (or, as the authors call it, Portunion 

 g. n.) msenadis, which is parasitic on the common shore-crab, being taken. 

 The history of each of these forms is considered in detail. In addition, 

 systematic summaries are given. 



* Comptes Rendus, cv. (1887) pp. 1130-2. 



t Arch. f. Mikr. Anaf., xxxi. (1S88) pp. 98-9. 



X 'Contributions a l'Etudc dos Bopyriens,' 4to, Lille, 1887. 



