ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 639 



family Tarsonemidse ; the body is segmented ; the mandibles are slightly 

 devL'hjped and sti let-like; tracheae arise at the base of the rostrum ou 

 the ventral surface; theie are two curious pi eminences, like adliesive 

 organs, between the first and second pairs of legs ; the first pair of limbs 

 are clawed ; there is sexual dimorphism. 



Even the young forms are of two distinct sorts ; in one set the clawed 

 first pair of limbs and the curious prominences are acquired, but the 

 three posterior pairs of appendages and the caudal setfe are lost. These 

 are females, and acquire sac-like bodies, distended with ova. embryo, and 

 young forms. Others seem to remain small and less modified, and are 

 pigmy males. The enigmatical prominences, the dimorj)liism, and the 

 extreme degeneration are interesting features in this new Acarid. 



f- Crustacea. 



Intestine of Decapoda and its Gland.* — Prof. G. Cattaneo has 

 followed up the researches of Weber, Frenzel, and others, as to the 

 structure of the intestine in Decapod Crustaceans, and the nature of the 

 mid-gut gland. In the intestine proper he distinguishes seven strata, 

 the chitiiious cuticle, a layer of cylindrical epithelium, a layer of con- 

 nective, longitudinal, radial and circular muscles, and an external 

 connective-tissue layer, but has added little to previous researches. His 

 experiments on the function of the gland are more interesting, for they 

 show that it is com])kx enough to be compared to that of all the 

 Vertebrate digestive glands taken together. The mid-gut gland thus 

 seems well to deserve the title he gives it of " polyenzymatic," which is 

 even wider than " hepato-pancreas." 



Early Development of Blastodermic Layers in Isopoda.-j- — M. L. 

 Eoule has investigated the early stages in the development of the 

 blastodermic layers in Aselhis aquaiicus and Porcellio scaher. In the 

 former fecundation is followed by the radial division of the yolk into a 

 small number of blastomeres, which, in their turn, divide radially and 

 tangentially to form a compact planula. The walls of the cells are very 

 delicate, and the least pressru'e causes them to disa; pear ; in sections these 

 walls are not seen and the whole yolk has the a2)pearance of a homo- 

 geneous mass, hollowed out by vacuoles, in the interior of which are 

 found the granulations dissolved by the reagents. Later on, a zone of 

 hyaline protoplasm appears at the pole of the egg, which con-esponds to 

 the anterior region of the embryo; this zone thickens, then seems to 

 slowly extend itself on the ventral and to rise up again to the dorsal 

 surface. The zone does not, however, extend by itself or indej^endently 

 of the yolk. In sections nuclei appear at the jjeriphery of the yolk ; 

 this part then becomes hyaline and the distinction between ectoblast and 

 mesoendoblast becomes apparent. 



The history of Porcellio is the same, save that there is no jH-ecedinfr 

 segmentation ; there is not, in fact, epiboly as one would expect from 

 Bobretzky's observations on the closely allied Oniscus. 



British Amphipoda. — In the second part of his paper J Dr. Norman 

 treats of the Leucothoidfe, Pardaliscidas, and Marine Uammaridfe. 

 Leucothoe imparicornis is a new species from Shetland ; LiUjehonjia 



* Atti Soc. Ital. Sci. Nat., xxx. (1887) pp. 238-72 (1 pi.). 



t Coiuptes EL-ndus, cix. (1889) pp. 78-9. 



X Ann. and Mag. Nat. Hist., iv. (1889) pp. 113-41, 3 pis. 



