ZOOLOGY AND BOTANY, MICROSCOPY. KTC. 45 



associated with marked concentration of the nervous system, which may 

 show a fusion of the second and third ganglia with the fourth. The 

 author holds the view that Pantopods are nearer to Crustaceans than to 

 Arachnids, and that Pantopods and Crustaceans have diverged from an 

 Annehd stock. . J. A. T. 



e. Crustacea. 



Respiratory Organs of a West Indian Land Crab. — C. C. Nuttinci 

 {Froc. Anier. Soc. Zool. in Anat. Pk,ecord, l'J20, 17, 350-1). In Ucides 

 caudatus, found at Antigua in a mangrove swamp, partly aquatic and 

 partly terrestrial in habit, the branchial chamber is divided into an 

 upper pulmonary portion and a lower branchial portion, the two separated 

 by a shelf attached to the branchiostegite. Three brush-like flagella 

 attached to the maxillipedes serve to moisten the edges of the gills. 

 The upper chamber is lined by a highly vascular membrane with villi. 

 On the body-wall proper, projecting into the pulmonary chamber, there 

 is a large turgid S-shaped Ijody (perhaps a big blood sinus) and a 

 number of enigmatical rigid capitate rods. This type seems to be 

 midway between Gecarcinus and Birgus. J. A. T. 



Permeability of the Gut in Crayfish and Snail. — H. J. Jordan 

 and H. J. Lam {Tijdschr. Ne.derland. Dierk. Ver., 191S, 16, 281-92). In 

 Astac'us there is a semi -permeable membrane lining the intestine ; in 

 Helix pomatia there is diffusion of salts and sugar in accordance with the 

 laws of osmosis. A gut may show (1) pure osmosis, (2) diosmosis or 

 diffusion, and (3) absorption. The last depends on cellular activity. 

 The absorbed material is found in vacuoles in the absorbing cells. So 

 far as is known they are never the same as the substances to which they 

 are changed by digestion. Foodstuffs are removed from the lumen of 

 the gut into the wall of the intestine, but not from the body cavity into 

 the gut. In the snail the special absorbing area is the mid-gut gland. 

 Glucose produced elsewhere by digestion may pass into other parts nf 

 the gut- wall, but this is not true absorption. In the mid-gut gland of 

 Astacus there is also true absorption. J. A. T. 



Studies on Oniscoidea. — Karl W. Verhoepf {Zoolog. Anzeiger, 

 1920, 51, 169-89). The term larva may be applied to the stages 

 between the throwing off of the embryonic sheath (long before the end 

 of the marsupial period) and the complete differentiation of the 

 principal parts of the seventh pair of legs and the first pleopod. It is 

 probable that all Oniscoidea have three larval stages. There is consider- 

 able diversity among species and considei'able variety within a species 

 (e.g. PorcelUo scalier) as regards the length of the embryonic de\^eloprnent 

 and larval stages. The brood-chamber or marsupium is made by five 

 pairs of brood-plates or ovostegites w^hich arise near the base of the first 

 five legs. It has a mechanically protective function, but it admits of a 

 large brood, it allows the brood to get advantage of the respiratory 

 current, and it prevents desiccation. It has very slight nutritive 

 significance. The cotyledons are evaginations of the delicate opercular 

 covering of the brood-sac and assist in the respiration. A marsupium 



