OF THE PnXTOZOA. 189 



Of the remaining genera, some comparative observations \\dll be made in pass- 

 ing, and particular researches respecting them added from Perty and other 

 inquirers. 



EufjJence and Astasice are mostly spindle-shaped (fusifomi), and give off 

 from theii' anterior extremity one or two delicate filaments, and posteriorly 

 a usually short blunt tail. Excluding the doubtful Euglenece, which, on 

 account of their rigid integument, we think, mth Dujardin, should be 

 transferred to another family, the remaining species of the two genera 

 in question are, from their inherent contractility, capable of varying their 

 form to a remarkable extent; i.e., to use a technical word, they are " meta- 

 holicJ^ This property is, nevertheless, much more restricted than in the 

 Amcebce ; for the Astasicea can send off no oifshoots or variable processes 

 like those animalcules, but in all their manifold contortions, elongations, 

 and contractions do not completely lose theii' primitive figure. In general, 

 the recurrence of the changes of figure is quite arbitrary and without regu- 

 larity. In Eutre])tia viridis and Astasia margaritifera, however, Perty 

 represents an alternate or peristaltic expansion and contraction of the or- 

 ganism, so that first the anterior and then the posterior extremity expands. 

 He adds, besides, that in this Astasia the contained clear globules are not 

 transferred backwards and forwards, but only a fluid matter which runs in 

 channels between them. 



The Astasicea are covered by a distinct flexible and elastic envelope, 

 which ]\Ii\ Carter calls the " pellicle," and states that it resembles the cover- 

 ing of Amcehce, is stnictiu'eless, and hardens after secretion. Stein also 

 afRi-ms that in Euglena it is similar to the enclosing membrane of Grvegarina, 

 and, like it, a shut sac without mouth or other aperture. On the contrary, 

 the translator of Kolliker's paper on Actinophrys (J. M. S. i. p. 100, note) 

 denies the existence of a distinct envelope to this genus. Beneath the 

 peUicle, adds Mr. Carter, is a transparent moving substance, with an inhe- 

 rent property of contractility and polymor})hism, which proves itself inde- 

 pendent of the superposed pelhcle when, in the process of encysting, the two 

 become separated : this substance is the " diaplianey 



Enclosed within these laminae are the contents, consisting of a proto- 

 plasmic matter with suspended particles and certain definite structures, viz. 

 a nucleus and contractile vesicle (XYIII. 46 «, c). The protoplasm is the 

 same matter Dujardin names the " sarcode," and is occupied with a varying 

 quantity of corpuscles, diff'ering among themselves in size, and imparting the 

 colour peculiar to the species. 



" In Euglena,^^ writes Mr. Carter {op. cit. p. 119), " the sarcode is separated 

 from the diaphane by a layer of pointed sigmoid fibres, arranged parallel to 

 each other, so as to fonn in Cnimemda texta (Duj.) a conical cell, which, so 

 soon as the ovules have become developed, and the diaphane and other con- 

 tents of the sarcode have died off, becomes transparent, although it still 

 retains its conical form until the resiliency of the fibres, now unrestrained 

 by the diaphane and other soft parts, causes dehiscence, and sets the ovules 

 at Uberty." 



These fibres are therefore the cause of the spiral markings of several 

 Emjhnce, as well as of Phacus and Chonemonas ; they are strongly marked 

 in Euglena spirogijra. " In another specimen of Euglena,^' says Perty (p. 57), 

 " of fully a sixth of a line in length, and of a grass-green coloiu% some thirty 

 dehcate longitudinal lines were perceptible, which, when the body turned on 

 itself, looked as if spii-ally disposed. Moreover, on examining Lepocinclis- 

 globules wheu partially diied, the spiral lines appear composed of rows of 

 closely aiTanged dots " — a phenomenon probably explicable on the supposi- 



