1420 Journal of Applied Microscopy 



Reconstructions were made in wax from serial sections, and very instructive 

 figures of these models are given in the plates. The author concludes that the 

 entoderm only is active in the formation of the gill-clefts. It is marked by 

 abundant mitoses, and by a thickening of the epithelium, and moves out to form 

 a junction with the ectoderm. The outer gill pockets appear only on first, fourth, 

 and fifth pairs, and are wholly of a secondary character, the ectoderm being 

 passively drawn in by the withdrawing entoderm of the throat pocket. The 

 closing membrane of clefts I to IV separates, but the openings are later closed 

 and the entoderm retreats from the epidermis. The aortic arches appear after 

 the formation of the gill pockets, arising as outgrowths from the dorsal, and later 

 the ventral aortae. The gill-clefts are thus in no way conditioned upon the 

 appearance of aortic arches. Six aortic arches appear, though in one case a 

 seventh vessel was found and in another instance the pulmonary (VI) was miss- 

 ing in the sixth gill-arch, and was found posterior to the sixth cleft. The deriva- 

 tives of the clefts are as follows : The first cleft, as usual, gives rise to the 

 middle ear and the eustachian tube. Epithelial buds from the dorsal ends of 

 clefts I-III form the thymus, while the fourth disappears entirely save for some 

 ephemeral epithelial corpuscles. The third cleft also gives rise to some similar 

 elements. The fifth cleft leaves no trace, but the sixth (on the left side only) 

 gives rise to the supra-pericardial body. All of these organs are of purely 

 entoder??ial origin, thus our author regards this last pair of throat pockets as 

 belonging to the branchial category, and concludes that the Laccrtilia have six 

 gill-clefts. The utility of these ephemeral embryonic organs is found (1) in 

 their relation to permanent organs (ear, thymus, supra-pericardial body) ; (2) in 

 their relation to the formation of the ganglia of the seventh, ninth, and tenth 

 cranial nerves. The fact that open clefts are found only in those amnota with 

 yolk-laden eggs (reptilia, aves, echidna) leads to the further suggestion that these 

 open clefts facilitate the passage of nutrient fluids from the yolk. c. a. k. 



Richardson, Harriet. Key to the Isopods of 'i^^ese papers of Miss Richardson's 



I hhe Atlantic Coast of North America, with dealing with the taxonomy of this 



■ descriptions of new and little known species. ., , i- . -i , , r • i 



^Proc.U. S.Nat. Mus. 23: 493-579, 1901. widely distributed group of animals, 



„. . ^ u . .. r. r ivT , are welcome aids for all who wish to 



Richardson, Harriet. Synopses of North 



American Invertebrates, VIII, The Isopoda. Study Isopods. The first paper is 

 Pt. I, Am. Naturalist, 34: 207-230; Pt. II, concerned only with species of the 

 ibid, 295-309, 1900. . -^ 



Atlantic Ocean and of our contiguous 



coasts. Synonomy, bibliography, geographical and bathymetrical distribution of 

 all the known species in this habitat are given, and fourteen new forms described. 

 The second paper includes keys to the fresh-water forms and the marine species 

 of all North America, with only the most general statements as to their 

 geographical distribution. c. a. k. 



Reighard, J., and Jennings, H. S. Anatomy of A laboratory manual of mammalian 



the Cat. pp. XX, 498. With 173 original anatomy, complete, of convenient 



figures drawn by Louise Burridge Jennings. . • .• ,1 1 



Henry Holt & Co., 1901. Size, approximating the general usage 



in terminology, and containing both 



description text systematically arranged and brief directions for preparations of 



