278 Infusorial Circuit of Qenerations. 



and watch the result. Practice will show the best power of quan- 

 tity and intensity to use. 



The use of a drop of Hquid necessitates the microscope being in 

 a vertical position : to obviate this inconvenience I have adapted a 

 rectangular prism, and turned the eye-piece part of the tube hori- 

 zontally, as in Amici's, and also made the prism to revolve con- 

 centric with the optic axis of the instrument, which enables several 

 persons sitting round the table to see the experiments at any 

 particular time by turning the eye-piece towards them. 



The light must be entirely reflected. By placing coloured glasses 

 in the diaphragm frame, and sending light through them from the 

 mirror, a clear outline is given to the crystals, and an illuminated 

 background, which produces an exceedingly beautiful effect. 



I am still pursuing the investigation, and hope to pubhsh 

 further interesting results. 



VII. — Infusorial Circuit of Generations. 

 By Theod. C. Hilgard. 



{Continued from p. 233, No. XXXV.) 



These " currant "-yolks enlarge in size, and soon at the (darken- 

 ing) circlet or rim of the introversion reveal a rapid rotation and 

 " ciliary motions," and still later, a contortion and volubility of 

 contents really perplexing to the attentive beholder, who in vain 

 attempts to determine its form, or at least to detect it in the moment 

 of hatching, "anxiously wasting whole nights and half days" 

 thereon, as Ehrenberg has expressed himself on a similar subject. 

 At last the membrane bursts and extrudes a globe or halo of 

 gelatine, containing a crucible-shaped body, gently moving, which, 

 when finally set free by the rupture of that gelatinous halo, at 

 once elastically extruding the inverted part, takes a shape resembhng 

 a rice-palea or the fore- wing of a thunder-fly (Thrips), travelling 

 broad-end foremost with great velocity and steady as an arrow. 

 After a while a somewhat ludicrous scene ensues, when the little 

 animal, by shedding its fissured skin or scabbard, is seen violently 

 struggling to disentangle its large jerking bristles hidden in the 

 veins of the sheath, and its small body. It thus appears like a 

 little dwarf, frantically floundering about in a Spanish cloak, spurs, 

 and sword too large for their owner. It now represents a very 

 small Oxytricha with comparatively very long, stout, but as yet 

 softish, bristles. 



This formed the more direct evolution from the Oxytricha 

 pellet, viz. out of its circular " currant- vesicles." Its enveloping 



