ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 939 



Some furtlier ilescription is also given of Pleocystidium parasitlcum, 

 found in the cells of Spirogijra, which he regards as belonging to no 

 recognized group, but most nearly related to the Chytridiacece. 



Cooke's Fresh-water Algae. — Dr. M. C. Cooke has now com- 

 pleted this excellent work, which no microscopist can be without. It 

 includes descriptions and coloured plates of all the fresh-water 

 algae at present found in the British Islands, exclusive of diatoms 

 and desmids. 



Alga in Solutions of Sulphate of Magnesia and of Lime.* — 

 Prof. E. Perceval Wright found a minute phycochromaceous alga in 

 test solutions of sulphate of magnesia and of lime and of phos2:)hate of 

 soda, which, in certain lights, presented quite a green shade. These 

 solutions were kept exposed to light, and were prepared with all due 

 care. The algal form abounded in all, but in the phosphate of soda 

 it developed much more rapidly, so as to present, on the solution 

 being shaken up, a dense flocculent cloud. The form seemed allied 

 to Chroococcus, and was immensely active in its cell-division and cell- 

 growth. 



Confusion between Species of Grammatophora.t — Dr. L. 

 Dippel points out that confusion has arisen in regard to the test 

 object Graramatophora marina, which he formerly described as 

 having 25 striae per 10 /a (now corrected by further examination to 22). 

 The species, however, which he examined under this name is not the 

 G. marina of W. Smith but of Kutzing, and he has satisfied himself 

 that the latter is identical with the G. oceanica of Ehrbg. 



It is therefore G. oceanica Ehrbg. to which the earlier descrip- 

 tions must be considered to apply, the name G. marina being reserved 

 for the more coarsely marked species of W. Smith, which has only 

 15 to 16 striie per 10 /x, as against the 22 stri^ of the former. 



There is also a very common confusion in the case of the rare 

 G. subtilissima (Bailey?), equally as difficult for a test object as 

 Fruslulia saxonica. The form supplied to most microscopists is 

 G. macilenta W. Sm., which in place of 34 to 36 striae per 10 fx has 

 only 25-28. 



Depth at which Marine Diatoms can exist.|— Count Castracane 

 adduces reasons, founded on physical and biological considerations, 

 for believing that the light of the sun may penetrate, in a very 

 rarefied condition, to greater depths in the sea than has generally 

 been supposed. The convex surface of the ocean enables it to be 

 regarded as an enormous lens which collects the solar rays, and 

 condenses them more or less in proportion to the convexity of the 

 surface and to the depth. Within the bodies of echini obtained in 

 the * Challenger ' expedition from latitude 41° 13' N. and longitude 

 65^ 45' W., at a depth of 1345 fathoms, or 2400 metres, the 



* Ann. and Maj?. Nat. Hist., xiv. (1884) p. 211. 

 t ZeitBchr. f. WL,a. Mikr., i. (1884) pp. 25-8. 



X Caatracane, Coiite Ab. F., ' Profondita cui giunge la vita dclle Diatomee 

 nel mare,' it", Roma, 1884, 9 pp. 



3 ii 2 



