228 



NA TURE 



[December 24, 1908 



borders of those seas. More than anything that is re- 

 quired, the paper says, is a new expedition on the same 

 lines as the Scotia, and Dr. Bruce is prepared to organise 

 such an expedition as soon as funds are provided. He 

 gives an outline of the way such an expedition might be 

 conducted and the work it might accomplish. 



We have been favoured with an advance copy of the 

 forty-seventh report of the Yorkshire Naturalists' Union, 

 containing an account of the proceedings at the forty-sixth 

 annual meeting held at Halifax on December 14, 1907, 

 and of the general working of the society during the past 

 year. Full reports are given of the condition of the bird- 

 life of the county, which are for the most part satisfactory, 

 although the numbers of the great grebe on Hornsea 

 Mere have been sadly reduced by the ravages of egg- 

 collectors. 



-At a recent meeting of the North Staffordshire Field 

 Club, Mr. F. W. Ash read a paper (of which we have 

 been favoured with a typed copy) on the evolution of the 

 cetacean tail-fin, in which it is attempted to rehabilitate 

 the generally discredited theory that this structure includes 

 vestiges of the hind-limbs as well as the tail itself. The 

 chief argument brought forward in support of the theory 

 appears to be based upon the expanded form and hori- 

 zontal position of the cetacean flukes, which is likened 

 to the complex formed by the hind-limbs and tail in seals. 

 The tendinous structures in the whale's flukes are con- 

 sidered to represent limb-tendons. 



We have received from the publishers, Messrs. Vinton 

 and Co., of Chancery Lane, a copy of the " Live Stock 

 Journal Almanac " for 1909, which is a wonderfully good 

 shillingsworth. The calendar portion contains ample space 

 for entering the dates of birth of farm and other animals, 

 while the rest of the volume is devoted to illustrated 

 articles on different breeds of domesticated animals in 

 1908 and kindred subjects, most of these articles being 

 by well-known specialists. Thus Shorthorns are discussed 

 by the late Mr. John Thornton, while Mr. .A. C. Beck 

 treats of shire horses. Special interest attaches to an 

 article by Sir Walter Gilbey on live stock a hundred years 

 ago, where much information will be found with regard 

 to the history and rise of many breeds. 



Three out of the four papers in No. 3 of the seventh 

 volume of the American Journal of Anatomy are devoted 

 to the Mammalia (other than man). Dr. Henry Fox treat- 

 ing of the pharyngeal pouches and their derivatives, Mr. 

 L. W. Williams describing the later development of the 

 notochord, and Mr. W. A. Baetjer discussing the mesen- 

 teric sac and thoracic duct in pig-embryos. In the second 

 of these the author finds that the primitive vertebra con- 

 sists of undifferentiated mesenchyma, which never under- 

 goes longitudinal segmentation, while the cartilage of the 

 actual vertebra arises, not from a primary condensation 

 of mesenchyma, but from a secondary condensation follow- 

 ing a loosening of the dense tissue of the scleromere, or 

 primitive vertebra. This secondary condensation of the 

 vertebra2 and intervertebral discs gives rise to pre- 

 cartilage. At this time the notochord expands slightly in 

 each vertebra, this being suppressed at the commencement 

 of chondrification, when most of the notochordal tissue is 

 forced into the intervertebral discs, where it forms the 

 nucleus pulposus. Primarily cellular and epithelial, the 

 notochordal tissue eventually becomes cellular, and then 

 closely resembles cartilage. 



The December number of the Popular Science Monthly 

 is one of unusual interest to naturalists, as it contains 

 NO. 2043, VOL. 79] 



the full text of Prof. W. Ridgeway's paper, read at the 

 last meeting of the British Association, on the applica- 

 tion of zoological laws to man ; an article on the aspects 

 of modern biology, by Prof. T. D. A. Cockerell ; and 

 one on the great Permian delta of Texas and its wonderful 

 extinct vertebrate fauna, by Dr. E. C. Case. The re- 

 mains of these animals are believed to have been carried 

 down by the Permian rivers in flood-time and entombed 

 in the mud of the delta. Restorations of several of the 

 reptiles are given, and it is Interesting to note that there 

 appear to have been two distinct types of the " fin-backed " 

 group, one of which (Dimetrodon) was carnivorous, while 

 the other (Naosaurus) was probably omnivorous. The 

 latter has perhaps the most wonderful dentition of any 

 known animal, the incisor teeth being sharp and chisel- 

 shaped, such as might be suited for cutting vegetable sub- 

 stances, while behind these are five pairs of sharp 

 triangular cutting-teeth, these being followed by simple 

 cones suited to holding a struggling victim. On the 

 palate and the opposing portion of the lower jaw are 

 heavy plates of bone covered by short, stumpy teeth of 

 a type found in mollusc-eating fish. In the author's 

 opinion, Naosaurus was probably omnivorous, but instead 

 of possessing a dentition of a generalised type, like that 

 of man or a pig, it had a special set of teeth for each kind 

 of food. 



The ichthyosaurs of the Trias, and more especially those 

 of North America, form the subject of an elaborate mono- 

 graph by Dr. J. C. Merriam, published as the first part 

 of vol. i. of the Memoirs of the University of California. 

 For several years past the author has been working at 

 these reptiles, and in the present memoir we have the 

 result of his labours. After a discussion of their distribu- 

 tion, the author proceeds to point out in what respects 

 the Triassic representatives of the Ichthyopterygia differ 

 from their successors of the Jurassic and Cretaceous 

 epochs. These differences consist, for the most part, of 

 less special adaptation to the exigencies of a purely aquatic 

 mode of life, thereby bringing them into closer connection 

 with less specialised land reptiles. What their terrestrial 

 ancestor may have been is, however, still unknown ; but it 

 probably existed at least as early as the Lower Trias. By 

 the middle portion of that period we find an undoubted 

 aquatic form — Cymbospondylus — which retains, however, 

 sufficient indications of affinity with a land form to give 

 a clue to the origin of the group. This reptile, it may be 

 presumed, had abandoned the shore as a regular dwelling- 

 place, but still resorted thereto on occasion, and probably 

 swam in shallow water in place of frequenting the open 

 sea. In contrast to this we have the highly specialised 

 representatives of Ophthalmosaurus and the closely allied, 

 if not identical, Baptanodon, which were evidently adapted 

 to play the part in the Jurassic oceans of the whales 

 of the present day. Even these, however, display great 

 simplicity of structure in all parts of their organisa- 

 tion except those specialised for swimming, and it is thus 

 abundantly evident that the ichthyosaurs trace their 

 ancestry to an extremely generalised type of reptile, while 

 it is equally clear that the group is one of the oldest in 

 its class. 



The whole of the November issue (vol. liii., part i.), 

 comprising 181 pages of text, is devoted to a paper by 

 Prof. A. A. W. Hubrecht on the early ontogenetic pheno- 

 mena in mammals, and their bearing on our interpreta- 

 tion of the phylogeny of the vertebrates, a paper to which 

 it is impossible to do adequate justice in the space at our 

 command. Naturally, the placenta and its modifications 



