110 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the Hammarby lake and ueiglibouring rocks at Danviken near Stock- 

 holm, of which several species and varieties are new. He gives also 

 general critical remarks on the families named above. 



The genus Scenedesmus is divided into two sections, the first of 

 which belongs to the true Pediastreae, while the second is nearly 

 allied to some species of Palmellaceae, as Baphidium and Selenastrum. 

 The following are given as their characters : — Sect. I. Obtusi. Cellula3 

 utroque polo plerumque obtusae vel rotundataa. Coenobium filiale 

 ruptura membranae cellulfe matricali liberum fit. Membrana cellu- 

 larum adultarum, cum membrana specierum Sectionis II. com- 

 parata, subcrassa. S. bijugatus, radiatus, alfernans,denticulaiu8 n. sp., 

 aculeolatus, Hystrix n. sp., dispnr, and quadricauda. Sect. II. Acuti. 

 Cellulae utroque polo plerumque plus minusve acutae. Propagatio 

 iucerta. Membrana cellularum adultarum cum membrana specierum 

 Sectionis I. comparata, tenuis. S. attenuatus and obliquus. 



The diagnosis follows of Adinastrum, a new genus of Palmel- 

 lacese : — Cellulae fusiformes, rarius fere obclavatae vel cylindricee, a 

 centro communi radiatim exeuntes, familias quadricellulares vel octo- 

 cellulares, libere natantes, formantes. Propagatio divisione succedanea 

 cytioplasmatis cellularum fit, et familia filialis eo mode formata 

 ruptura membranae cellulae matricalis libera fit. Zoosporae ignotse. 

 Only species A. Hantzschii; long, cell, 10-24 /x; crass. 3-6 /ix. 



The previously unknown mode of reproduction of Selenastrum is 

 thus described. In S. acuminatum n. sp. the cell-contents first divide 

 lengthwise into two halves, the two daughter-cells again dividing by 

 an oblique wall. These four cells sometimes directly constitute 

 themselves into a new coenobium, but usually only after another 

 division, in which case either the whole eight cells may form a new 

 coenobium after the bursting of the membrane of the mother-cell, or 

 they may constitute two coenobia of four cells each. Selenastrum 

 forms a connecting link between the Pediastreae and Palmellaceae. 



In Urococcus insignis Kiitz., (^Chroococcus macrococcus) (3 ferru- 

 gineus Lagerh., neither the stipes nor all the integuments of the cell 

 are coloured blue by chlor-iodide of zinc, but usually only the inner- 

 most of the latter. 



The formation of new coenobia of DictyospJioermm reniforme takes 

 place by each mother-cell dividing by repeated bipartition into eight 

 daughter-cells, all the membranes of the original coenobium and of 

 the stipites being absorbed. In D. Ehrenbergianum and pulchellum, 

 on the contrary, the mother-cells only divide into four daughter-cells 

 arranged in a cross, which then separate, and finally form new coenobia 

 by repeated bipartition. 



Crenothrix Kiilmiana as a Contaminator of Water.* — The 

 water which supplies Lille, from the springs at Emmerin, having 

 become undrinkable in consequence of a red deposit and foetid taste 

 and smell, was found by A. Giard to be infected with Crenothrix 

 Kuhiiana, which precipitates oxide of iron from aerated water. He 

 found the microgonidia formed by transverse division in the sporangia 



* Comptes Kendus, xiv. (1882) p. 247. 



