58 SCIENCE PROGRESS 



is the title of a suggestive paper which deals not only with 

 these structures in Craniate Vertebrates, but also with 

 Hatschek's pit in Amphioxus, of the structure and development 

 of which a detailed account is given. It seeks to homologise 

 these with the " proboscis pore " of Balanoglossus and the 

 water pore of the Echinoderm, all being of the nature of ccelo- 

 mostomes. The homology of the premandibular somites of 

 the Craniates with the anterior coelomic sacs of Amphioxus 

 is pointed out. It is concluded that the hypophysis of the 

 Craniata is represented in Amphioxus by the wheel organ 

 situated in front of the true mouth, and that its original function 

 was probably to drive food into the alimentary canal. 



Watson has dealt with " The Evolution of the Tetrapod 

 Shoulder Girdle and Limb (Journ. of Anat. vol. lii. Oct. 191 7). 

 Any one who has had to deal with the shoulder girdle and limb 

 of the higher vertebrates is immediately confronted with a 

 great deal of confusion and inconsistency. This paper is 

 welcome, since it attempts to give a satisfactory account, from 

 the evolutionary point of view, of the changes undergone by 

 that region from the lowest to the highest forms. The matter 

 is dealt with under two headings ; the first treating of the 

 actual facts and their interpretation and the second of the 

 functional significance of the changes described. A large 

 series of forms both recent and fossil are dealt with, including 

 a wax-plate model reconstructed from a series of sections of 

 an 11 '5 embryo of the marsupial Trichosurus. The way in 

 which the girdle and limb of such a form as Eryops can be 

 derived from those of a fish is indicated. The coracoid element 

 of the Lizards, Sphenodon, Chelonia, and Birds is homologised 

 with the precoracoid, as is also the epicoracoid of Monotremes. 

 The omosternum of the Theria is considered the equivalent 

 of the old reptilian interclavicle. In early forms, e.g. Pely- 

 cosaurs, the humerus is only able to move parallel with the 

 ground with a backwards and forwards motion being at right 

 angles to the body in its middle position. A steady change 

 from this condition to that in Cynognathus, where the humerus 

 " moves in a vertical plane at an angle of about 45 ° with the 

 animal's length," is demonstrable. 



Other papers include : " Descriptions of new Fishes from 

 Lake Tanganyika forming part of the Collection made by the 

 late Dr. L. Stappers for the Belgian Government," by Boulenger 



