386 NATURAL SCIENCE. May. 



tissues chiefly affected ; of complex anomalies, like hermaphroditism, 

 apparent or real ; and of monsters single or double. The illustrations 

 are very useful, and as appropriately horrible as the subject demands. 

 There is an index ; full table of contents ; and glossary of terms. 



Altogether it is a most useful book, and is to be commended to 

 all anatomists and embryologists. P. C. M. 



The Embryology and Metamorphosis of the Macroura. By W. K. Brooks, 

 Professor of Animal Morphology in the Johns Hopkins University, and F. H. 

 Herrick, Professor of Biology in Adelbert College. National Academy of 

 Sciences, vol. v., Fourth Memoir. Pp. 325-576, with 57 Plates. 



In this beautiful memoir the authors have made a notable contribu- 

 tion to knowledge of the development of the Macroura. Animals 

 which, like the Crustacea, pass through a series of successive moults 

 during their larval life, naturally exhibit a series of gradations leading 

 towards the adult condition. P'ritz Miiller and Claus showed that 

 in this group a very large number of orders, families, genera, and 

 species display the relation between ontogeny and phylogeny. At 

 the same time, Claus pointed out that an equally large number of 

 adaptive larvae are to be found, and in the introduction to this 

 memoir Dr. Brooks strongly insists on the necessity of careful and 

 exhaustive study in each case before the significance of a larval 

 history can be understood. The survival of larvae living free in water 

 depends on their adaptation to their present environment, and so 

 recapitulation of ancestral stages in the present metamorphosis must 

 depend to a large extent on the persistency of those external condi- 

 tions to which the larvae were originally adapted. 



The chief forms studied in this memoir are Stenopus hispidiis, 

 Alpheus, and Gonodadyliis chivagra. In addition to anatomical and 

 embryological detail, a number of side issues of general interest turn up. 

 Thus one would expect (says Dr. Brooks) that the least specialised 

 species are the most widely diffused. But the larvae of Stenopus 

 Jiispidus, although Stenopus is one of the most highly specialised of the 

 Crustacea, are most widely distributed. Specimens from the Indian 

 Ocean and the South Pacific agree with those from the West Indies 

 down to the most minute marking. " It is well protected from 

 enemies by a thorny armour of hooked spines which cover all the 

 upper surface of its body and limbs, and, as all the hooks point 

 forward, the attempt of an enemy to swallow a Stenopus must be 

 difiicult and painful." 



Many of the species of Alpheus live as parasites in the canal of 

 sponges, and individuals of the same species living in different species 

 of sponges may differ greatly in colour and habits. 



In Alpheus and in Stenopus, after impregnation takes place, the 

 nucleus divides and a syncytium of eight nuclei is found. In Alpheus 

 there is a slight invagination and a modified gastrula is found. But 

 in all the accounts of development given readers will be struck by the 

 want of distinctness in the separation and formation of the germinal 

 layers. It certainly seems as if the familiar successive origins of the 

 germinal layers are present only in a very vague manner in this 

 group. 



The account of the larvae of Gonodactylus chivagra is specially 

 valuable, as so little is known of the Stomatopoda. In the present 

 work, Dr. Brooks is able to confirm most of the results he reached 

 in the " Challenger " monograph. 



