NOTICES OF BOOKS. xi 



to be readily discerned and often to be clearly recognisable during life, 

 but it must be stated that, judging from the figures, they do not very 

 closely resemble the centrosomes of such h'gher plants and animals in 

 which these bodies have been clearly identified. 



The most remarkable statements in the book are those which refer 

 to the origin and structure of the spindle. This body is said to arise 

 from the centrosome as a rounded structure, which eventually assumes a 

 cylindrical form, and then penetrates the nucleus, travelling towards it 

 as a perfectly definite entity. When it reaches the interior of the 

 nucleus it increases in size and the chromosomes ultimately become 

 arrayed around it, in a manner similar to that which has been described 

 for some protozoa. The original centrosome, after having budded off 

 the spindle, finally degenerates and new ones are formed from the ends 

 of the spindle towards the close of mitosis. It is suggested that the 

 daughter-chromosomes are attracted chemeotactically towards the poles 

 and are not pulled thither by the contraction of a peripheral mantle of 

 spindle fibres. After the separation of the constituents of the two 

 daughter-nuclei, a cell-wall gradually advances from the periphery, 

 cutting the entire cell into two parts in essentially the same fashion as 

 has been described by Strasburger and others for, e.g., Spirogyra. 



After the account of the process of nuclear division, which is illus- 

 trated by many beautiful figures, the author proceeds to discuss the 

 mode of movement prevalent amongst Diatoms and concludes that 

 locomotion is effected by means of the emission of a mucilaginous sub- 

 stance throught the slits in the shell. 



Enough has been said to show that the book teems with new 

 observations and it is to be hoped that other investigators may also be 

 attracted to so promising a field of research as the Diatoms clearly 

 afford, and such is also the desire expressed by the author himself, who 

 thereby proves himself to be superior to that commercial instinct, occa- 

 sionally to be met with even amongst scientific men, which prompts 

 them to keep to themselves any promising lines of investigation on 

 which they may have lighted lest some one else should happen to 

 infringe on their paltry claims to priority. 



