ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 221 



account is given of the external structure of the body and its append- 

 ages. Apart from size, endless diversity of colour-markings, and 

 slight deviations in the mandibles and maxillae, very few variations were 

 met with in the large number of specimens examined. In Idotea baltica 

 there is remarkable power of individual colour change. The author 

 describes /. sarsi sp. n., and, for reasons given, replaces the generic name 

 Stenosoma by Synisoma. Besides Idotea and Synisoma, the author 

 includes in his British representatives the genus Zenobiana. Most 

 Idoteids live among masses of decaying algae, and feed on dead fishes, 

 molluscs, crustaceans, annelids, etc. Their chief enemies are fishes. 



Variation of the Appendages bearing Pseudo-tracheae in Terres- 

 trial Isopods.* — Walter E. Collinge finds considerable diversity in 

 regard to these structures in different examples of the same species. 

 They are not suited for generic or specific distinction. In Oniscoida 

 the appendages in question are plate-like in structure, with the ex- 

 ception of the sixth. Each consists of an inner plate, the endopodite, 

 which functions as a branchial organ, and an outer plate, the exopodite, 

 which covers and protects the former. In some genera, e.g. Porcellio, 

 PorcelUonides, Cylisticus, ArmadilUdkim, and Eluma, air tubes, or pseudo- 

 tracheae, are present in the outer plate on the first and second appendages, 

 and sometimes on the three succeeding ones as well. In a single species, 

 e.g. ForcelUo f ictus, there is considerable variety as to the number of 

 appendages in which the air-tubes occur. 



Idotea lacrustris.f — Walter E. Collinge discusses the structure and 

 generic position of Idotea lacustris Thomson. The species should be 

 referred to Richardson's genus Pentidotea, which combines the posses- 

 sion of a five-jointed palp of the maxillipede with the presence of a 

 nietasome of only three segments. Hitherto the genus has been 

 known only from the Northern Pacific ; but Thomson's species were from 

 a fresh-water stream, Mt. Mihiwaka, Otago, and from Dunedin Harbour 



Amphipoda montagui.* — H.Chas. Williamson describes an amphipod 

 which he proposes to call Amphipoda montagui (M.-Edwards). It is the 

 same as Isxa montagui M.-Edwards. Specimens were found on lobsters, 

 lurking about the maxillipedes and middle ventral line of the thorax. 

 "In order to attain the principal objects of classification (which are 

 (1) given the name of the animal to find the description, and (2) given 

 the animal to find out the name which has been attached to it), the 

 sub-division of the animal kingdom does not require to be carried out 

 on a scale beyond that which makes Amphipoda a descriptive name. 

 If the species here dealt with had been named Amphipoda montagui, all 

 zoologists would have known something about it, whereas under 

 Edwards' name, /sae« montagui, it is altogether unknown to ninety-nine 

 out of one hundred zoologists." 



* Journ. Zool. Research, i. (1916) pp. 159-60. 



t Journ. Zool. Research, i. (1916) pp. 153-7 (1 pi.). 



\ Journ. Zool. Research, i. (1916) pp. 135-49 (29 figs.). 



