ZOOLOGY AND BOTANY MICROSCOPY, ETC. 57 



of each, and supplies diagnoses of five which had been issued with name 

 only by C. Muller. Dixon calls attention to the exceeding difficulty 

 attached to New Zealand bryology, owing to the creation of numerous 

 new species by C. Muller, W. Colenso and R. Brown (of Christchurch), 

 and the impossibility of obtaining authentic specimens. 



North American Sphagnum.* — A. Le R. Andrews treats of the 

 section Acisphagnum, which shows a high development in its structure, 

 It is divisible into Squarrosa, Cuspidata, Acutifolia. In Squarrosa he 

 includes S. Angstromii Hartm., S. teres Angstr., S. squarrosum Crome ; 

 and shows how, by their cell-structure and the shape of their leaves, 

 they may be distinguished from one another and from other species. 



Thallophyta. 

 Algae. 



(By Mrs. E. S. Gepp.) 



Oceanic Plankton. f — H. H. Gran contributes a chapter on the 

 plankton collected on the ' Michael Sars ' expedition, to the report of 

 that voyage lately published. He used a steam centrifuge capable of 

 centrifuging 1200 c.cm.' of sea-water at a speed of 700-800 revolutions 

 per minute, thereby discovering that the minute nannoplankton is far 

 more abundant than the larger plankton. He found also that pelagic 

 life is most abundant at depths of 10-20 metres, but becomes extremely 

 scanty below 100 metres ; and he agrees with Natkaiisohn that marine 

 plant life thrives best where ascending currents bring upward a supply 

 of nitrogenous compounds derived from the decomposition of organic 

 matter in the deep sea. Grau also finds that tropical collections of 

 plankton show that the species are numerous and mostly rare, whereas 

 in colder waters there are few species but great aggregations of indi- 

 viduals. 



Diatoms in Sea-urchins. :j: — CI. Antonelli records fifty-three species 

 of diatoms which he found in the digestive tract of sea-urchins collected 

 at Irani on the Adriatic. The predominant species belonged to Limno- 

 phora and Sgnedra. Gocconeis and Navkula were also abundant, as 

 well as species of Pleurosigma, Hyalodiscus, Biddulphia, and Surirella. 

 Among the rare genera were Goscino discus, Gerataulus, Actinoptychus, 

 Amphora, and Grammatophora. 



Nuclear Division in Spirogyra.§ — M. L. Merrirnan writes on 

 nuclear division in Spirogyra rrassa. He finds that : — 1. A spireme 

 originates from material derived from both nucleolus and nuclear net- 

 work. The materials constituting this spireme are aggregations varying 

 in appearance, in number, and in staining capacities. 2 These aggre- 

 gations are not the chromosomes. They greatly exceed in number that 



* Bryologist, xvi. (1913) pp. 59-62, 74-6. 



+ Murray and Hjort, The Depths of the Ocean. London: Macmillan, 1912, 

 Chap. vi. 



X Att. Pontif. Ace. Rom. Nuov. Line, lxvi. (1912-13) pp. 25-33. 

 § Bot. Gaz., lvi. (1913) pp. 319-30 (2 pis.). 



