454 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



the " dark " aud " clear " cells. The former are only found in the basi- 

 podite, and their form varies in different species ; the pale cells may 

 be found in any of the joints, and in the upjier ones their duct always 

 remains distinct. The details of various genera are entered into, and 

 the " thread-like web " in the Corophiidse, the origin of which 

 Mr. Spence Bate was unable to determine, is shown to be a product 

 of these gland-cells. 



The unicellular glands of OrcJiestia are formed on another type, 

 the intracellular cuticular tubules have a relatively wider lumen, and 

 are correspondingly less numerous ; the glandular apparatus is, 

 fui'ther, not so centralized, for they are found over the whole of the 

 body, and their duct may open on the body- wall by a proper pore. 

 Those on the appendages are more especially described, and it is 

 pointed out that they are similar in character in the two sexes ; 

 OrcJiestia, it is to be noted, is more terrestrial in habit than its allies, 

 and it is possible that the secretion of the glands protects the gills 

 from drying too rapidly. 



The penal glands of the CreveftinidcB are appended to the hinder 

 region of the enteron, where tbey form a paired arrangement, consist- 

 ing of two tubes, which are diverticula of the tract ; differing as they 

 do in details in the different genera, they would appear to occupy con- 

 stantly the same position, just in front of the commencement of the 

 rectum ; being outgrowths of the end of tbe mid-gut, they cannot be 

 regarded as the homologues of the Malpighian vessels of insects. 

 When least modified, as in Melita, they are unpaired. After 

 describing the differences seen in various genera, the author states 

 that the amount of concretion which may be collected in them is very 

 great in Orchestia, whereas in the rest there are no solid excretory 

 products. 



The rectum of Orchestia presents some peculiarities ; it extends 

 throughout the whole length of the abdomen, and is divisible into two 

 portions, the hinder of which corresponds to the rectum of its allies. 

 In the front portion the epithelial layer is higher in its dorso-median 

 portion ; at the sides of this ridge there are two epithelial folds, 

 while an unpaired fold arises from tbe ventral surface ; the whole is 

 lined by a thick cuticle, marked by longitudinal ridges, each of which 

 is beset with a row of fine cuticular setee, which ajipear to aid in the 

 removal of the fpeces. The investing musculature is divided into two 

 lateral parts, and the fibres do not run longitudinally, but obliquely, 

 so as when contracting to act both as circular and as longitudinal 

 muscles. The hinder portion of the rectum does not essentially differ 

 from that of the other Crevettinidce, except in the great development of 

 its epithelium. This elaborate arrangement is jDrobably to be asso- 

 ciated with some unknown peculiarity in the feeding of Orchestia. 



The gills of Orchestia also present some peculiarities ; they form 

 small, relatively thick and strong plates, which are attached from the 

 second to the sixth pair of thoracic legs ; the two lamellae of the 

 hypodermis are widely separated, and contain a far larger cavity than 

 is to be found in Gammarus ; they consist largely of broad cylindrical 

 cells, with rounded large nuclei ; in parts the matrix is considerably 



