1897. SOME NEW BOOKS. 199 



The Polyzoa conclude the volume. Mr. Harmer bases his 

 account on British species solely, regarding them as amply represen- 

 tative, a statement which hardly applies to the Cyclostomata. The 

 controversy as to the name of the class is alluded to ; many English 

 writers are certainly inclining to Ehrenberg's name Bryozoa. The 

 Entoprocta are rightly retained as one of the two chief divisions of 

 the class. The brown body of the Ectoprocta, the derivation of the 

 avicularium and vibraculum, and the morphology of the larva are 

 explained; and the view that the fresh-water Phylactolasmata are not 

 primitive forms, as usually stated, is put convincingly. The 

 references to the palaeontology of the class are scanty : e.g., Ulrich's 

 work on American Palaeozoic forms is passed over; Walford's results 

 are accepted as trustworthy, whereas he seems to have mistaken 

 accidental scratches and the like for structural features ; existing 

 families of Cyclostomata commence before the Jurassic period, even in 

 British Silurian and American Carboniferous strata. There are two 

 useful tables for the identification of British fresh-water and marine 

 species respectively. As to the latter, the student should bear in 

 mind the caution given on pp. 515-16 concerning the form of the 

 colony, especially as to encrusting and erect forms. Note that 

 Epistomia, and not Notamia, is the correct generic name for the species 

 biirsaria (p. 526). 



Consideration of the whole volume suggests a few general 

 remarks. There is a certain vagueness, sure to puzzle the non- 

 professional student, in the use of the terms body-cavity and ccelom^ and 

 the connections in which they occasionally appear. Not that it is 

 confined to this work ; still, it could easily be avoided. The absence 

 of brief definitions to the principal groups, such as are given in the 

 companion volume on Arthropoda, is a misfortune. They certainly 

 conduce to clearness of ideas, and are indispensable in certain stages 

 of knowledge. Classificatory terms are also used in a somewhat 

 haphazard fashion. For instance, the Platyhelminthes constitute a 

 phylum with three branches, whilst the Nemathelminthes are not desig- 

 nated, and are divided into three sub-orders ; the Rotifera and Polyzoa 

 are classes ; the Chaetopoda are not designated, and are divided into 

 four orders, one of which is the Oligochaeta (p. 241) ; but the 

 Oligochaeta on p. 347 are termed a division of the order Chaetopoda, 

 whilst the Hirudmea, apparently co-ordinate with Oligochaeta, are 

 divided into two sub-orders. Such things ought not to be. Finally, it 

 is remarkable how sparing is the use of the word " worm," whilst the 

 term Vermes — the term under which the whole contents of the 

 volume were at one time classified — is mentioned, and with a touch 

 of scorn, but once. A prefatory introduction would have been a 

 good thing : it might have explained many essential points and 

 removed difficulties. 



Seasonal Dimorphism. 



Neue Versuche Zum Saison-Dimorphismus der Schmetterlinge. Von Dr. 



August Weismann. Abdruck aus den Zoologischm Jahrhiichern, Abth. f. Syst. 



Bd. viii. Jena: Fischer, 1895. 

 New Experiments on the Seasonal Dimorphism of Lepidoptera. By Dr. 



August Weismann. (Translated from the German by W. E. Nicholson, F.E.S.) 



Reprinted from The Entomologist, Jan. -Aug., 1896. 



Dr. Weismann's essay should be another reproof to those ill-informed 

 persons who cry out on its author as a pure speculator. The 

 misconception is natural ; for his theories have reached everyone, 

 even politicians, while the exact laborious work that has accompanied 



