296 



not by mineralization of the enamel-cells^ but by mineraliza- 

 tion of a substance exuded from those cells. The dentinal 

 processes or tlii'eads extend through the whole length of the 

 dentinal tubes, and through their branches. The dentine- 

 cells do not calcify, nor is the dentine produced by the calci- 

 fication of such cells. Interglobular spaces may produce the 

 appearance of a lamellar disposition of the dentine, but are 

 not, as was once thought, the result of a true lamellification. 

 The s^^litting up of the dentine by weathering into lamellse 

 does not depend on interglobular s^^aces. The ivory of the 

 elephant's incisor, in which the concentric lamellae are so 

 often seen, possesses no interglobular spaces. 



Microzoology — On the Structure of the British Nemerteans, 

 and some new British Annelids. By W. Carmichael Mcin- 

 tosh, M.D., F.L.S. — This magnificent work, which the Royal 

 Society of Edinburgh has done honour to itself in producing, 

 is the result of the employment of holiday time and the few 

 hours of leisure of a busy medical man in charge of a county 

 lunatic asylum. Thirteen plates illustrate the memoir, which 

 occupies more than a hundred quarto pages, and is of great 

 value throughout. Dr. Mcintosh is well known as a writer 

 on the anatomy of invertebrata ; he is the author of a work 

 which the Ray Society is to publish on the British annelids 

 and nemerteans, in Avhicli the species Avill be carefully dis- 

 cussed and figured. To judge by the drawings he has 

 exhibited at meetings of the British Association, and by 

 those in the present work. Dr. Mcintosh's volume will be 

 one of the most beautiful ever produced on zoological 

 matters. In the paj)er published by the Royal Society of 

 Edinburgh the anatomy and histology of species of Omma- 

 toplea, of Borlasia, of Cephalothrix, of Tetrastemma, and 

 Lineus, is given with the greatest minuteness, the Avorms 

 having been studied very closely under the microscope 

 by means of transverse sections. The writings of Rathke, 

 Max Schultze, de Quatrefages, Claparede and Kcferstein, 

 and of Harry Goodsir, Johnston, and Dr. Williams, are 

 thoroughly examined by Dr. Mcintosh and most minutely 

 criticised ; he differs very considerably from all of them on 

 many important jDoints of the anatomy — especially as to the 

 structure of the proboscis and its sheath ; and from the great 

 care he has bestowed on the investigation he is in a position 

 to really decide the questions Avhicli he has taken ujj. The 

 development of some forms is also given. We observe 

 Pylidium of Midler quoted without a reference to Prof. Yan 

 Beneden's recent declaration that the supposed metagenesis 

 in this case is a parasitism, the worm being quite distinct really 



