232 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Navicula rhomboides.* — E. M. Nelson discusses the old question of 

 Navicula rhomboides and the Amician test, and points out the differences 

 between the diatoms regarded as N. rhomboides in England and America 

 respectively. Two other varieties of the species are discussed. The 

 author suggests that the minute variations of the various forms might 

 be expressed in numbers, and the numerical index of each would be a 

 great aid to identification and comparison. The economic value of 

 Diatoms is alluded to, and the fact that they form the food of Copepods 

 which in turn are devoured by fish. 



Desmidiaceae of Bohemia. f — J. Lutkemiiller gives a list of about 

 280 species of Desmids found in Bohemia, including new species and 

 varieties. Remarks are made on Penium and Roya. Some of the 

 species of Penium are here placed under Cosmarium as being more 

 closely allied with that genus. Roya has hitherto been considered as 

 belonging to Closterieae, on the strength of the shape of its cells, 

 since details as to the cell-membrane and cell-division were wanting. 

 Lutkemiiller has, however, been able to procure material, and to make 

 the following observations : 1. The cell-membrane is hyaline, slightly 

 refractive and entirely without structure ; under the highest magnifica- 

 tion, neither in stained nor unstained preparations is any segmentation 

 to be observed, and it is also free of pores. 2. Cupric ammonium 

 bydrate causes an immediate fading of the cell-membrane, which 

 becomes flaccid and in a few minutes dissolves away. 3. During cell- 

 division a transverse wall is formed which takes its origin solely from 

 the membrane of the mother-cell ; there is no previous separation of 

 the halves of the cell-membrane, nor any intercalation of a newly formed 

 membranous ring. After the splitting of the dividing wall into two 

 sheets, there follows speedily the separation of the daughter-cells, when 

 the young halves of the cell have hardly taken on a hemispherical form. 

 Even at this stage it is impossible to demonstrate a dividing line between 

 the young and the old halves. It is thus to be seen that the genus Roya 

 must be transferred from the Closterieae, and placed with the Saccoderm 

 Desmidiaceae in the tribe Spirotaenieae. The nearest ally to Roya is 

 Mesotseniwn Naeg. As regards the pores in the cell-membrane of 

 Glosterium, the author has re-examined species which he had previously 

 declared to be without pores, and also a series of the smallest species in 

 the tribe Cosmariea?, and he finds that every one of them possesses 

 pores. He believes now that there are no species of Cosmariea? without 

 pores. 



New African Species of Volvox.j — G. S. West describes two new 

 species of Volvox collected respectively in Rhodesia and from the Albert 

 Nyanza. Two species are also recorded from Australia, one of which, 

 though probably new, cannot be described for want of adequate material. 

 The author gives some interesting notes on the two European species, 

 V.globator and V. aureus, and contrasts the respective characters of each 

 species in tabular form. 



* 



Journ. Quekett Micr. Club, ser. 2, xi. (1910), pp. 93-8. 

 t Verb., k. Zool.-Bot. Ges. Wien, lx. (1910) pp. 478-503 (2 pis., figs, in text). 

 J Journ. Quekett Micr. Club, ser. 2, xi. (1910) pp. 99-104 (1 pi.). 



