672 



SYSTEMATIC HISTORY OF THE INFUSORIA. 



1-30" in length, the head has become 

 triangular (xxxvii. 11), and thus it gra- 

 dually takes on the perfect form. The 

 yoimg had previously crept about in the 

 gelatinous investment of tlie parents ; 

 they now begin to " swarm," uniting 

 together by their caudal extremities, and 

 are readily pressed out as free-swimming 

 colonies, resembling in this state the 

 genus Conochilus (Huxley). But, besides 

 the ova whose development is thus de- 

 scribed. Professor Huxley observed a 

 second class, to which he refers as fol- 

 lows : — "In a fully-grown Lacmularia 

 which has produced ova, the ovary, or a 

 large portion of it, begins to assume a 

 blackish tint (xxxvii. 22); the cells, 

 with their nuclei, undergo no change, 

 but a deposit of strongly refracting ele- 

 mentary granules takes place in the pale 

 connecting substance. Every transition 

 may be traced, from the deep black por- 

 tions to unaltered spots of the ovarium ; 

 and pressure alwa3'S renders the cells 

 with their nuclei visible amongst the 

 granules. The investing membrane of the 

 ovary becomes separated from the dark 

 mass, so as to leave a space ; and the outer 

 surface of the mass invests itself vA\\\ 

 a thick reddish membrane (xxxvii. 24), 



which is rough, elastic, and reticulated 

 from the presence of many minute aper- 

 tures. This membrane is soluble in both 

 hot nitric acid and caustic potass. The 

 nuclei and cells, or rather the clear spaces 

 indicating them, are still visible upon 

 pressm-e, and may be readily seen by 

 bursting the outer coat. By degrees the 

 ephippial ovum becomes lighter, until at 

 last its colour is reddish-brown, like that 

 of ordinary ova ; but its contents are now 

 seen to be divided into two masses, hemi- 

 spherical from mutual contact (f. 21). If 

 this body be now crushed, it will be f oimd 

 that an inner structureless membrane 

 exists within the first-stated membrane, 

 and sends a partition inwards at the line 

 of demarcation of the two masses. The 

 contents are precisely the same as before, 

 viz. nuclei and elementary granules. I 

 was unable to trace the development of 

 these ephippial ova any fm-ther." 



Professor Huxley thus indicates his 

 belief in the existence of two classes of 



thinks probably requires sexual fecunda- 

 tion, whilst the others do not. Cohn 

 believes that the bodies usually termed 

 ova by Huxley and others are not so, 

 but internal gemmae. 



Genus MELICERTA (XXXII. 386, 387 ; XXXVI. 1 ; XXXVII. 12-18)- 

 — With a case or envelope ; solitary ; rotary organ simple, with four lobes 

 when expanded ; free longitudinal muscles for the contractions of the body ; 

 alimentary canal divided into segments, in one of which (the pharyngeal 

 bulb) are complex jaws ; mouth situate at the bottom of the cleft between 

 the two larger lobes of the rotary organ ; the orifice of the cloaca near the 

 junction of the long peduncle mtli the body. Male generative organization 

 unknown; believed by Mr. Gosse to be dioecious. Female organs a large 

 ovary filled with granular protoplasm and germinal vesicles, as in the pre- 

 ceding genus, but with a distinct oviduct opening into the cloaca. Two 

 water-vascular canals, arising from a contractile vesicle, ascend towards the 

 head. Two tactile appendages, with setigerous extremities, on each side the 

 head. Two eye-spots in the young animal. Nervous system uncertain. 



Melicerta ringens. — Case (xxxvi. 

 1 d) conical, granulated, resembling a 

 honey-comb, of a brownish-red colour; 

 it is composed of small lenticular bodies, 

 secreted and deposited by the animalcule ; 

 these are agglutinated by a peculiar 

 viscid matter, afterwards hardened in 

 the water. Into this tulie the soft cry- 

 stalline or whitish animalcule can with- 

 draw itself; and when its flower-like 

 wheel-work (la) is expanded, the vibra- 

 tile cilia appear to run along the margin of 

 this organ ; but, in fact, each single cilium 

 only turns itself upon its base, their aggre- 

 gate motion causing a little whirlpool in 



the water, directed towards the mouth, 

 which is situated in the middle of the two 

 large leaflets of the rotary organ; the eyes 

 in the young animal are placed near the 

 two other bent leaflets, which, according 

 to Ehrenberg, are analogous to a cleft 

 upper lip of the dorsal surface : the dis- 

 charging orifice is on the same side; and 

 therefore the dorsal tail-like portion be- 

 comes a ventral member or foot, (xxxii. 

 386, an animalcule within its case, having 

 the rotary organ contracted ; fig. 387, with 

 the trochal disc fidly expanded : the case 

 is given in outline only, in order to 

 show the internal structure. ) On Lemnae 



