902 



SCIENCE. 



[N. S. Vol. XVI. No. 414. 



determined. The plates accompanying this 

 memoir were drawn by the author in his usual 

 clear and artistic manner. They represent 

 just what is intended to be shown, and are 

 evidently dej)ictions of natural objects. 



Conldin's embryology of Tereliratulina sep- 

 ientrionalis (2) presents an excellent illustra- 

 tion of the results obtained by modern 

 methods. Owing to the opacity of tlie em- 

 bryos and to the absence of serial sections, 

 good microtomes and other accessories, Morse 

 during 1871-73 was able to show mainly the 

 external modifications in the developing em- 

 bryo. His observations, however, were very 

 thorough and complete. 



Conkliii describes in detail the egg and its 

 cleavage, gastrulation and the formation of the 

 body layers and cavities, the orientation of the 

 embryo, and the development and organiza- 

 tion of the larva. 



The constrictions of the cephalula, hitherto 

 supposed to mark distinct segments, are shown 

 to be produced by the anterior and posterior 

 mantle furrows, but at no time do they form 

 true septa dividing the coelom. The author, 

 after reviewing the real and supposed resem- 

 blances between the larval and embryo brach- 

 iopods and other organisms, concludes that 

 the relationship between Plioronis, the 

 Bryozoa, and the Brachiopoda, is suificiently 

 close to warrant their being placed in the same 

 phylum, though not in the same class. 



All our knowledge regarding the embryol- 

 ogy of the Brachiopoda has hitherto practically 

 been confined to the group known as Artic- 

 ulata. The work of Yatsu (3) is, therefore, 

 of great interest and value, since it relates to 

 Lingula, the living and ahnost unchanged 

 representative of the most ancient types. The 

 developmental characters of Lingula are in 

 many respects quite different from those of 

 any brachiopod previously studied. The 

 three-lobed cephalula stage of the neoembryo, 

 so characteristic of Gisiella, Lacazella and 

 Terehratulina, is not developed in Lingula, 

 which does not attain more than a two-lobed 

 condition. Also, the posterior lobe is not the 

 caudal as in those genera, but constitutes the 

 thoracic division. Cistella, Lacazella, etc., 

 imdergo a metamorphosis in passing from the 



neoembryonic to the typembryonic condition, 

 consisting of the reflexing of the mantle lobes 

 forward over the anterior division. This 

 change is absent in Lingula, and the mantle 

 lobes simply grow anteriorly. This difl^erenee 

 has an especial significance in the develop- 

 ment of the shell, for in Cistella, etc., the shell 

 is developed from what was originally the 

 inner side of the mantle lobes, while in 

 Lingula it is secreted by the outside. The 

 author further considers that the pedicle is 

 embryologically and morphologically distinct 

 from the pedicle of the articulate brachiopods. 



The embryonic and early post-embryonic 

 stages are fully described, together with full 

 details and illustrations of the various organs 

 and structures. As a whole, no single species 

 of brachiopod has heretofore received so com- 

 plete and extended treatment along these lines 

 of research. 



The two other papers by this author (4, 5) 

 relate to the histology and habits of Lingula. 

 New facts are given, showing the extraordinary 

 power of resistance to unfavorable conditions, 

 which has doubtless been a potent factor in 

 preserving the genus since Cambrian times. 



It is noteworthy that in all the standard 

 literature on the Brachiopoda no notice has 

 been taken of the earliest American publica- 

 tion relating to the anatomy of these animals. 

 It is contained in a ' Text-book of Vegetable 

 and Animal Physiology,' by Henry Goadby, 

 published in New York in 1858. One chap- 

 ter is devoted to the nutrition in the Brach- 

 iopoda and another to a description of their 

 nervous and circulatory systems. Inasmuch 

 as Goadby's observations were based upon 

 original dissections and studies, their claims 

 for a place in the literature of brachiopod re- 

 search are perfectly valid. (._ -^ Beecher. 



General Investigations of Curved Surfaces. 

 By Karl Friedrich Gauss. Translated 

 with Notes and a Bibliography by James 

 C.\DALL MoREHEAD, A.M., M.S., and Adam 

 Miller Hiltebeitel, A.M. The Princeton 

 University Library. 1902. Quarto. Pp. 

 viii -f 127. 

 By the liberality of the Princeton Library 



Publishing Association and the alumni of 



