ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 97 



swarmed actively, not coming completely to rest in some cases for 

 sixteen hours. The resulting zygosperm (zygote of Strasburger) then 

 rounds itself off, and begins to germinate. No morphological 

 differentiation whatever could be detected in the zygospheres before 

 conjugation. 



Sexual Reproduction of the Bangiacese.* — The statement of 

 Eeinke that in these Algae the amcBboid spores are impregnated by the 

 spermatia, has been shown to be incorrect by Goebel. G. Berthold 

 has now followed out the process of fertilization more completely. 



The small spermatia (poUinoids), which have long been known in 

 the case of Porphyra, attach themselves singly or in numbers to the 

 surface of the thallus, over the centre of the cells. At first spherical 

 and membraneless, they become somewhat flattened, and, while closely 

 adherent to the thallus, become coated with a delicate cell-wall. By 

 means of a slender thread of protoplasm they then bore through the 

 cell-wall of the thallus, nearly the whole of the contents passing into 

 the cell. The result of this impregnation is that the contents of the 

 cell break up into eight spores (oosperms), which move about, on 

 escaping, in an amoeboid manner. In some cases the female cells 

 (oogonia) put out on both sides trichogyne-like protuberances, the 

 contents of which are used up in the formation of the spores. 



The author has also seen non-sexual spores of Porphyra, somewhat 

 larger than, but otherwise resembling the oosperms. 



These observations induce Berthold to assign the systematic 

 position to the Bangiacese as the lowest class of Florideae. From 

 Bangia and Porphyra there is a gradual transition through Balbiana 

 and the NemaliesB to the typical Florideae, and the peculiar structure 

 of Lemanea and Dudresnaya. 



Cladothrix and Sphserotilus.f — In the sediment of vessels con- 

 taining water, B. Eyferth found abundance of filaments of Stereonema 

 Ktz., mixed with stems of Anihophysa. The tubular Stereonema fila- 

 ments were covered with threads, which broke up at the extremities 

 partly into bacteroid fragments, and partly manifested false dichoto- 

 mous branching. These were identified with Cladothrix dichotoma 

 Cohn ; and the author states that between this and Sphcerotilus natans 

 Ktz. there is a complete series of intermediate forms, although the 

 extreme forms differ greatly, depending on an abundant or defective 

 supply of nutriment. The Sphcerotilus is an extremely useful organism 

 in purifying impure water. 



Sycamina nigrescens, a Volvocinea destitute of Chlorophyll.l — 

 M. Van Tieghem has examined the black or dark deposit found on 

 the surface of pond-water or at the bottom of aquaria, and finds it to 

 be composed of a minute blackish alga, destitute of chlorophyll, and 

 living on the organic matters the decomposition of which it promotes. 



In its mature condition this organism consists of minute spherical 



* MT. Zool. Stat. Neapel, ii. (1880) pp, 78-82. See Bot. Ztg., xxxviii. (1880) 

 p. 701. 



t Bot. Ztg., xxxviii. (1880) pp. 673-6. 

 X Bull. Soc. Bot. France, xxvii. (1880) pp. 200-4. 

 Ser. 2.— Vol. I. H 



