ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 175 



horses ? It is still too soon to answer this question ; but I venture to 

 think that if we should, by and by, arrive at the conclusion that our 

 domestic horses have had a multiple origin — -have sprung from at least 

 two perfectly distinct sources — we shall probably subsequently come to 

 the further conclusion that our big-headed, big-jointed horses, with 

 well-marked chestnuts on the hind legs, are more intimately related to 

 the wild horse than the small-headed, slender-limbed varieties without 

 chestnuts on the hind legs ; that, in fact, the heavy horses, whether 

 found in Europe, Asia, or Africa, and Przewalsky's horse have sprung 

 from the same ancestors." 



Coloration of the Quaggas* — E. I. Pocock has an interesting 

 essay on the coloration of the "quaggas," — i.e. zebras of the type 

 commonly known as Burchell's. The coloration of the coat renders a 

 zebra invisible under three conditions, namely, at a distance on the 

 open plain at mid-day, at close quarters in the dusk and on moonlight 

 nights, and in the cover afforded by thickets. Pocock analyses the 

 various factors which contribute to this " procryptic " result. The pro- 

 tective value is so great that it seems unnecessary to seek for any other 

 interpretation. 



Plankton of Scottish Lakes. j — James Murray contributes some 

 notes on the plankton of the lakes of the Tay basin, samples of which 

 were collected in the course of bathymetrical survey undertaken by 

 Sir John Murray and Mr. Laurence Pullar. Of almost constant occur- 

 rence at all seasons are DiajJtomus gracilis, Cyclops strenuus, Daphnia 

 lacustris, Bosmina obtusirostris • two species of Conochilus, Anurma 

 cochleare, Notholca longispina ; and the Diatom, Asterionella gracillima. 

 In the summer, Holopedium, Leptodora, Bythrotrephes, and Polyphemus 

 are as generally distributed. Only less common are Asplanchna prio- 

 dontctj Polyarthra platyptera, Peridinium tubulatum, Ceratium hirundi- 

 nelta, Mallomonas. The rotifers, Floscularia pelagka and Notops 

 pygmmis, are of frequent occurrence ; a not very dissimilar association 

 is found in small ponds, but the species are for the most part different ; 

 thus Diaptomus is represented by 1). castor, Daphnia by D. pidex, 

 Bosmina by B. cormtta ; Rotifers and Algse will be more abundant and 

 varied, and there will probably be some Ostracods. Even the smallest 

 lochs surveyed had the plankton distinctly lacustrine, but a few nearly 

 or quite stagnant lochans showed a slight approach to the pond type. 

 In some forms, e.g. Daphnia lacustris and Bosmina obtusirostris, there 

 is great variability. The phenomenon of Wasserblut, usually due to 

 Alga?, may also be due to Protozoa and to Rotifers, — on one occasion 

 to the rather uncommon Rotifer, Dinocharis collinsii. Many details 

 are given as to individual lochs. 



Ceylonese Cephalochorda4 — W. M. Tattersall reports on a collection 

 made by Prof. W. A. Herd man. Although no new species are recorded,, 

 the fact that seven species (including var. belcheri) occur around Ceylon, 

 indicates the great wealth of the Acraniate fauna of these waters. 



* Nature, lxviii. 1903, pp. 356-7 (1 tig.). 



f Scottish Geogr. Magazine, xx. (HiOl) pp. 41-7. 



X Rep. Pearl Oyster Fisheries Ceylon. Sappl. Report vi. pp. 200-26 (1 pL> 



