578 



SYSTEMATIC HISTORY OF THE INFUSORIA. 



all the Peridiuiaea, and (says Pei-ty) not 

 a variety of P. cornutum, as Ehrenberg 

 thought : the lorica is rather concave 

 below, and less bent than in that species. 

 Empty loricse are clearly areolate, and 

 the areolae round. A red stigma is often 

 seen in the posterior half. The anterior 

 supports a single horn, and there are 

 three behind. 1-120" to 1-96." 



P. arcticum (Ehr.) resembles P. ina- 

 croceros, but is- stronger, and has its 

 large horns all curbed and three or four 

 times longer than the body; surface 

 rough, ^^dth little raised puncta or spines. 

 Length of body, 1-48"', of entire being 

 1-18"'. It is phosphorescent, and found 

 at Kingston Bay, Ne^^^folmdland, with 

 P. Fiirca, P. Tridcns, and P. divergens. 



P. longipes (Bailey). — Body triangular, 

 rough ; angles produced into very long 

 ciliated processes, of which the two 

 fi'ontal ones are longest. Body crossed 

 obliquely by a ciliated gTOOve (xxxi. 23). 

 St. George's Bank, New York. 



j P. depressum (Bailey). — Lorica ob- 

 liquely depressed, with one large conical 

 posterior process, and two smaller conical 

 frontal processes; the latter separated 

 by a deep notch. Surface granular and 

 reticulated. Both this and the precedino- 

 species, which were found together, were 

 doubtless furnished with a proboscis 

 when living, and, like other marine 

 species of this genus, were probably 

 phosphorescent. The form of P. depres- 

 sum is closely analogous to the embryo 

 of Nereis, whose curious changes were 

 studied by Loven (and referred to in 

 Prof. Owen's Lectures on the Inverte- 

 brata, ed. 1843, p. 147). This account of 

 Nereis, and particularly the comparison 

 of Prof. Owen's figure with the Peridi- 

 nium depressum (xxxi. 21, 22), led Dr. 

 Bailey to suspect that at least a portion 

 of the forms now included in the genus 

 Peridinium might be imperfectly-deve- 

 loped or embryonic Annelida. 



Genus GLENODINIUM. — Peridinia with motile cilia placed in a trans- 

 verse furrow or zone, and provided with an eye. The organization is much 

 the same, in other respects, as that of the preceding genus. In G. cinctum a 

 flabellum is seen to emanate from the middle, and to vibrate Kke the wreath 

 of cUia. It is also probably present in the other species, though hitherto 

 .unobserved. The lorica is combustible. Vacuoles and fine granules are 

 visible in all the species ; the former are veiy distinct in G. apicuJatum. The 

 red speck is in the form of an elongated or horseshoe-shaped spot, and 

 constitutes the essential character of the genus. Longitudinal self-division 

 has been observed only in G. cinctum. 



Although this genus is rejected by Dujardin as indistinguishable from 

 Peridinium, yet Perty retains it, making its point of separation from the 

 latter genus — which, by the way, he prefers to call Ceratium — consist in the 

 absence of horns to the loiica. The red speck he ignores, equally with Du- 

 jardin, as a distinctive character. In this way Perty's Glenoclinmm=- Peri- 

 dinium, without horns, of Ehr. 



Glenodinium cinctum— Peridimmn | G.(Peridimum)Alpimmi(PeYty). — The 

 oculatum (Duj.). — Oval, or nearly sphe- j sculptm'ing of the surface is indistiact; 

 rical ; smooth ; stigma large, semi-lunar, j and very frequently there are, alternately, 



and transverse. In fresh water, amongst 

 Oscillatorise. 1-570". It is seen both 

 with and without a red speck. 



G. tabulatum. — Oval; yellowish-green; 

 lorica granular and reticulate with ele- 

 vated lines, but not spinous; truncate 

 and denticulate posteriorly, and biden- 

 tate anteriorly. 1-570" to 1-430". 



" The colour," says Perty, " is mostly 

 brown, especially in mature specimens, 

 and more rarely brownish-green or gi-een. 

 A red stigma is but rarely present." 



colom-ed masses of granules and hyaline 

 spaces aroimd the border of the lorica, 

 producing a notched appearance. 1-430". 

 It is probably only an Alpine variety of 

 G. tabulatum, in which the lorica has not 

 attained its perfect structure. On Mount 

 St. Gothard, and in Lake Lugano. 



G. apiculatum. — Oval ; yellowish- 

 green; lorica smooth, but with hispid 

 furrows on the margin, as shown in 

 X. 226. The stigma is oblong, and ex- 

 tremities obtuse. Amongst Confervje. 

 1-570" to 1-430". 



