318 Bibliograpliical Notice. 



from the raidst of the series, viz. in the region of the original 2ijd, 

 5th, and 7th transverse rows. 



The second and longest communication is by Dr. Willey himself, 

 on " Enteropneusta from the South Pacific, with Notes on the West- 

 Indian species." After a few introductory remarks Dr. Willey 

 proceeds to a synopsis of the families and genera of Enteropneusta, 

 recognizing in the group three families: the Ptychoderida?, Spenge- 

 lida?, and Balanoglossida?. Next comes the systematic description 

 of several South-Pacific species, including three not previously de- 

 scribed, and some notes on the AVest-Indian forms, with descriptions 

 of two new species. Finally, under the heading of " Morphology 

 of the Enteropnensta," there is a lengthy discussion of the various 

 features of the group which betray a reUitionship with the Chordata. 

 In the specific descriptions, which are very full and careful, and 

 in chide remarks on tlie colour and oocology of the animals, very 

 great attention is paid to internal features. 



The pages devoted to theoretical questions are beyond doubt a 

 most important contribution to the discussion on the vexed question 

 of the ancestry of the Chordata. The matter is divided into nine 

 heads, dealing respectively with the gill- slits, the proboscis pores, 

 the origin of the vertebrate kidney, the nervous system, the fate of 

 the genital pleuras of Enteropneusts, the neurenteric canal of 

 vertebrates, the notocliord, the branchial bars, and the endostyle. 

 Throughout the discussion the dominating idea is that of the 

 change of structure of an existing organ with its change in function. 

 An origin de novo is not postulated for any structure, but a number 

 of characteristic chordate features are derived from pre-existing 

 enteropncustan organs, on the supposition of a change of function. 



It is not possible here to do more than touch shortly on each 

 of the heads we have mentioned above, but some indication of 

 Dr. Willey's views on these points will probably be welcome to many. 

 In treating of the gill-slits it is sought to show that they were at 

 first unlimited in number and coextensive with the gonads, the 

 oxygenation of which, and not respiration, was their primary 

 function. In the second section, on the proboscis pores, it is 

 claimed that the pore-canal of the proboscis of Enteropneusta is 

 homologous with the neuro-hypophysial canal of the ascidiau larva 

 (the " primordium " of the adult subneural gland), the proboscis pore 

 being here represented by the pore leading from the neurohypo- 

 physial canal into the cerebral vesicle. In Amphioxus the 

 proboscis pore-canal has become Kolliker's olfactory pit, into which 

 the neural canal opens by the neuropore. The view that the 

 preoral pit of the larva represents the left division of the head- 

 cavity is upheld, and the latter is compared with the left proboscis 

 coelome of the Enteropneusta. The opening of the preoral pit to 

 the exterior represents the communication between the ccelome and 

 the pore-canal. The nephric tubules oi AmpMo.vus {andL so of the 

 Chordates) are derived from a series of " regional pore-canals " 

 continuous with that comprising the proboscis, collar, and truncal 

 pores (proto-, mcso-, and opisthoraeric pores). It will be seen that 



