926 



SYSTEMATIC HISTORY OF THE INFUSORIA. 



Genus BERKELEYA (Grev.). — Frustules na\iciiloid, linear-lanceolate, 

 included within tubular submembranaceous filaments, which are free at 

 their extremities, but immersed below in a more or less definite tubercle. 

 Marine. Berkeley a differs from Schizonema in having the base of the fila- 

 ments immersed in an orbicular gelatinous tubercle. This tubercle is at first 

 firm and definite, but finally, especially when growing on rocks, becomes 

 enlarged, soft, and often somewhat indefinite. 



Berkeleya fragilis (Grev.). — Fila- 

 ments subsimple, minute ; frustides 

 crowded, slender, lanceolate or linear- 

 lanceolate, with the striae obsolete or 

 wanting. GBF. p. 416 ; SD. ii. p. 67, 

 pi. 54. £ 344. On Zostera, Algae, and 

 rocks. Em-ope. The gelatinous tubercle 

 diu'ing growth becomes attenuated and 

 more dilFused, and sometimes forms an 



indefinite slimy covering about the base 

 of the filaments. In a dried state this 

 species acquires a metallic lustre. 



B. Adriatica (K.). — Filaments branch- 

 ed ; branches distinctly subdi-sdded ; frus- 

 tides narrowly linear-lanceolate, rather 

 obtuse. I^. p. 109, pi. 22. f 4. Adriatic 

 Sea. (xiv. 34, 35.) 1-300". Scarcely 

 distinct from B. fragilis. 



Genus COLLETONEMA (Breb.). — Frustules naviculoid, arranged in series 

 within a tender, simple or divided, filiform or globose frond. Aquatic. 

 According to Professor Smith, " the freshwater habitat and slightly divided 

 frond distinguish the present genus from Schizonema; and [he adds] the 

 frustules are also more firmly sihceous than those of that genus, and the 

 character of the valve can usually be well seen after maceration in acid." 

 Professor Kiitzing describes CoUetonema as having a filiform frond composed 

 of series of naviculae held together and enveloped by an amorphous gelatinous 

 mucus, without an exterior gelatinous tube. We doubt if any of the above 

 characters sufficiently distinguish CoUetonema from the allied genera, because 

 they are either inadmissible in generic definitions, uncertain, or not pecuhar 

 to the genus. The absence of an external tube, if constant, would be of 

 generic importance ; but we sometimes find the frustule contained within an 

 evident (although tender and evanescent) tube, whilst in Micromega, on the 

 other hand, the presence of an external tube is sometimes doubtful. The 

 fronds are exceedingly tbin and tender, readily permitting the escape of their 

 frustules, which may then be mistaken for species belonging to other genera ; 

 thus Professor Smith remarks that it is possible that Pinnularia radiosa may 

 be merely the free state of CoUetonema neglectum, and Navicida crassinervia 

 the same condition of C. vulgare. 



CoLLETONEMA exwiium (Thw., K.). 

 — Frond filiform ; frustide in lateral 

 view sigmoid, striated. KA. p. 891 ; 

 SD. ii. p. 69, pi. 56. £ 350. = Schizonema 

 eximiimi, ANH. 1848 ; Gloionema sig- 

 moides, EB. 1845 ; Encgonema sigmoides, 

 KA. p. 62. ? Britain, Demerara ? Valves 

 linear, sigmoid from the ends sloping in 

 opposite directions ; striae 56 in -001". 

 (VIII. 43.) 



C. viridulum (Breb.). — Frond filiform ; 

 naviculae spirally and densely arranged ; 

 valves lanceolate, rather obtuse, smooth ; 

 front view linear-oblong, slightly and 

 gi'adually attenuated towards the trun- 

 cate apices. KA. p. 105. France. 



C. lacustre (Ag., K.). — Frond filiform, 

 simple or subramose, finer than a hair, 

 enclosed in an imperceptible membrane ; 

 naviculae elliptic or parallelogramic, in 

 a single or double series. KSA. p. 105. 



= Schizonema lacustre^ Ag CD. p. 18. 

 Sweden. Tufts erect, brownish yellow; in 

 size and habit like Sphacelaria cirrosa. 



C. vidgare (Thw.), — Frond filiform, 

 simple or divided, gradually taperiug, 

 containing one or two regular rows of 

 frustules ; valves oblong-lanceolate, with 

 slightly contracted, obtuse ends. SD. ii. 

 p, 70, pi. 56. f. 351. = Schizonetna vidgare, 

 ANH. 1848. England and France. Less 

 common, according to Professor Smith, 

 than the next species. Striae 72 in -001". 



C. neglectum (Thw.). — Frond slightly 

 divided, obtuse, containing numerous 

 and closely packed frustules ; valves lan- 

 ceolate, with obtuse ends. SBD. ii. 

 p. 70, pi. 56. f. 352. = Schizonema neg- 

 lectum, ANH. 1848. England. 



C. subcohcsrens (Thw.). — Frond glo- 

 bose, gelatinous, pervaded by hregular 

 rows of frustules; valves oblono-, with 



