RECENT ADVANCES IN SCIENCE 47 



grenfelli Chilton," by Chilton (ibid.) ; " Barnacles from the 

 Hull of the Terra Nova " (ibid. Feb. 191 7), "On the Struc- 

 ture and Function of the Mouth-parts of the Palaemonid 

 Prawns" (Proc. Zool. Soc. Feb. 191 7), both by Borradaile ; 

 and " The Embryonic Development of Trichogramma evanescens 

 Westw. ; Monembryonic Egg Parasite of Donacia simplex 

 Fab.," by Gatenby (Quart. Jour. Micro. Sci. vol. lxii. Feb. 191 7). 



Vertebrata. — Very useful additions have been made to our 

 knowledge of the development of the lower Chordata. By 

 the publication of " A Note concerning the Collar Cavities of 

 the Larval Amphioxus," Smith and Newth (Quart. Jour. Micro. 

 Sci. vol. lxii. Feb. 191 7) throw considerable light on this 

 somewhat vexed question and render it possible to compare 

 the collar cavity in this form with the mandibular cavities 

 present in the embryos of Petromyzon and the Elasmobranchs, 

 and their results and conclusions have been accepted by Mac- 

 Bride, from whose former conclusions they differ. Certain further 

 details in the early development are dealt with in a paper " On 

 the Development of the Cape Cephalodiscus (C. gilchristi Ride- 

 wood) " by Gilchrist (ibid.), who has been able to work on early 

 stages fixed in a variety of ways. After an indeterminate 

 cleavage a blastula stage occurs which later becomes solid. 

 The gastrula-like condition is reached in a somewhat complex 

 way without any typical invagination but by the formation of 

 a lumen in the yolk-mass which then becomes connected to a 

 posterior involution. Further points in the formation and 

 fate of the body - cavities and of the larval nervous system 

 are described, so that several gaps left by previous workers are 

 now filled in. 



Other papers include : "A Revision of the Clupeid Fishes 

 of the Genus Pellonula and of Related Genera in the Rivers of 

 Africa," and " The Fishes of the Genus Clupea," both by Regan 

 (Ann. and Mag. Nat. Hist. Feb. 191 7) ; "The Prechordal 

 Portion of the Chondrocranium of Chimcera collieri," by Allis 

 (Proc. Zool. Soc. March 20, 191 7), and " The Early Develop- 

 ment of the Spleen of Lepidopterus and Protopterus," by 

 Purser (Quart. Jour. Micro. Sci. vol. lxii. Feb. 191 7). 



Watson has furnished " A Sketch-classification of the Pre- 

 Jurassic Tetrapod Vertebrates " (ibid.), which is based on a 

 consideration of all parts of the skeleton of the Amphibia and 

 Reptilia of that period. The characters are divided into two 



