1897. SOME NEW BOOKS. i97 



hermaphrodite : it is not the case that no females occur in the 

 alternate generation (p. 151), or that there is parthenogenesis (p. 161). 

 The Rotifera have always proved attractive to the non-pro- 

 fessional naturalist. There are, however, certain difficulties in their 

 anatomy, and these are clearly elucidated in Professor Hartog's 

 account of the class. The varieties of trochal disc, the structure of 

 the mastax, reproduction, and habits are fully dealt with.^ The 

 classification is modified somewhat from Hudson and Gosse's, and 

 the Professor broaches a new and interesting idea as to the zoological 

 affinities of the class, bringing it "into close relationship with lower 

 Platyhelminthes," especially the Pilidium larva ; he rejects any 

 affinity to Crustacea. 



The four orders, Archiannelida, Polychaeta, Myzostomaria, and 

 Ohgoch^eta, are ranged by Dr. Benham under the term Chsetopoda : 

 he deals with the first three. The remarkable genus Dinophilus is 

 included, apparently with some reluctance, in the order first-named ; 

 Saccocirrns is omitted, and the interesting Histviohdella ]iomav[ relegated 

 to a foot-note. In the account of Polygordius no mention is made of 

 the development of the excretory system, neither is its trochosphere 

 figured ; indeed, this important larval form is nowhere treated 

 adequately in this volume. 



Nereis pelagica (fig. 4) is described as a type of the Polychaeta, but 

 the description is too much interrupted by facts of general anatomy. 



Fig. 4. — Nereis pelagica, nat. size. 



The classification of the order adopted is the one proposed in 1894 

 by Dr. Benham ; but any difficulties owing to its recent character are 

 minimised as far as possible by the full account to which chapter xii. 

 is devoted. Certain errors {inter alia) in general anatomy may be 

 noted. The septa of the body are not so complete as to isolate the 

 compartments from one another, and the parapodia are essentially 

 hollow organs, facts not explicitly stated ; prostomial tentacles are 

 probably not restricted solely to the sub-order Nereidiformia, e.g., 

 according to Mayer, the tentacles of Spio may be prostomial ; the 

 modified chaetse of Capitella are confined to the male, and modified 

 anterior chsetse occur in other Polychaeta ; all polycirrids are devoid 

 of a vascular system, and, in Capitella, some, not all, of the ccelomic 

 corpuscles are red ; the siphon is found in some Eunicidae as well as 

 in Capitellifovmia; the longitudinal nephridial duct of some Terebelhdae, 

 e.g., the common Lanice conchilega, is omitted ; Capitella has one pair 

 of gonoducts, other genera of the family more than one pair ; Haplo- 

 branchus is not hermaphrodite. A whole chapter (chapter xi.) is 

 devoted to a resniiie of the natural history of the order. 



Turning to the Oligochaeta, the order is for once treated with 

 complete justice, and by its monographer, Mr. Beddard ; the 

 Hirudinea are brought into intimate relation with it, the diff"erences 

 between the two being, as he says, neither so "numerous" nor so 



