536 Reviews. [July, 



between believing that the motile ciliated unicellular plants are endowed 

 with a will ; or that a will is one of the characteristic attributes of 

 animals only, from the highest to the lowest. It is not our intention 

 further to discuss the subject here, it only shows how interesting is 

 the study of these lowly forms of life. The author believes that the 

 Infusoria are provided with urticating organs somewhat similar to 

 those of the Hydro-Medusae, and he describes them with great minute- 

 ness. The sponges, he considers, possess the first approach to muscular 

 fibre, and for this reason, amongst others, he places them at the head 

 of the class Protozoa. His observations lead him to believe that he has 

 found Spermatozoa in sponges ; the reader will, however, be disposed 

 to agree with him that further investigations are needed to confirm 

 the fact. Finally, he explains the method in which he believes the 

 beautiful sponge spicules to be produced ; having discovered in many 

 of them a central core, which he says he has seen protruding beyond 

 the barrel of the spicule, and which, he thinks, forms the nucleus 

 that serves as the basis of its development. 



In directing the notice of our English microscopists to this 

 beautiful work of Professor Kolliker, by far the best handbook of 

 the Protozoa extant (if its shape will admit of its being called a 

 handbook), we cannot help regretting that more attention has not 

 been paid in England to the forms of which it treats. It is true that 

 the history of the Foraminifera, and to some extent that of the 

 sponges, are the fruits of British intellect, but the commonest types 

 of Protozoa, and those most easily accessible, have been sadly neglected 

 by our biologists, whom we should be glad to see rank side by side 

 with Continental observers in this branch of Zoological science. The 

 investigation of these forms will throw fresh light upon the whole 

 question of species. Do any of our investigators fear to approach the 

 subject, lest the results should " unsettle " their minds ? If so, it 

 will always be left to foreign microscopists, who are less impressible 

 in that respect. 



The present work, which presents, as we have already said, by 

 far the most complete epitome of the anatomy and physiology of the 

 Protozoa, forms the first of a series, which is to embrace the whole 

 animal kingdom, and the well-known labours of the author leave 

 little doubt that the remaining portions of his task will be executed 

 with equal ability. We presume that arrangements will be made to 

 translate each section of the publication as it appears ; meanwhile such 

 of our readers as are able to study it in the original tongue will 

 do well to possess themselves of what promises to be an invaluable 

 series of " Histological Sketches." 



