OF THE HYDATIN^EA. 



683 



ova large, smooth j winter ova spinous. 

 1-40". 



According to Cohn, the male of this 

 species (xxxix. 8) is a small Rotifer 

 1-20"' in length. Body short and sac- 

 cular ; two short toes, usually retracted ; 

 head distinguished by a slight excava- 

 tion, and with an ear-like lappet on 

 either side ; rotary organ furnished with 

 some stout uncini, in addition to the 

 fine cilia ; pharynx cj'lindiical, contain- 

 ing two scalpel-like teeth, which can be 

 extended beyond the mouth; stomach 

 separated from the mtestine by a con- 

 striction. A contractile vesicle above the 

 foot, but water-canals scarcely visible. 

 A cerebral ganglion, resembling a long 

 sac, within the head, and bearing a red 

 speck at its anterior extremity. Males 

 and females usually existing in the same 

 Volvox. We have considerable doubts 

 respecting the correctness of the above 

 accoimt, since it diifers so widely from 

 what has elsewhere been observed 

 amongst such male animals as have 

 hitherto been discovered amongst the 

 Rotifera. The absence of a complete 

 alimentary canal has hitherto character- 

 ized all male Rotifera. (The female is 

 represented after Cohn in xxxix. 9.) 



N. petromyzon. — Elongated, attenu- 

 ated at both ends; mouth and rotary 

 organ lateral. Ehrenberg says, in May 

 1835 he found one in a Volvox Glohator, 

 whose gemmiferous masses it eats like 

 N. parasitica. The eggs are often de- 

 posited on Epistylis. 1-180" to 1-144". 



N. lacinulata \Vorticella aiiriculata et 

 arcinulata, M.). — Small, conical, trun- 

 cated and slightly lobed in front ; teeth 

 extended, often bicuspid. Alimentary 

 canal, according to Eeydig, clearly sepa- 

 rable into a greenish yellow stomach 

 and a clear intestine. This species is 

 very active. Found with Chlarnidomonas 

 Pulviscidus in clear water, also in water- 

 tubs. 1-280". 



N. forcipata. — Small, elongated ; toes 

 long, and often crossed ; eye very large. 

 The vibratile organ appears sometimes 

 like a simple wreath. Amongst Lemnae. 

 Very common in Switzerland, according 

 to Perty, but with a small red eye-speck 

 instead of a large pale one, as described 

 by Ehrenberg. 1-180". 



N. coUaris. — Elongated, large, gradu- 

 ally attenuated at both ends ; neck tur- 

 gid; toes short. It swims slowly, the 

 vibratile organ being small in comparison 

 vAih. the body. 1-48". 



N. JVerneckii. — Elongated, gi'adually 

 attenuated at both ends ; toes short. It 



has two setae near the mouth. This 

 animalcule resembles N. coUaris, but is 

 smaller, and lives in the club-like ex- 

 crescences of Vaucheria as an entophyte. 

 1-90". 



N. Najas. — Conical, cylindrical, stout, 

 truncated in front ; no auricles. It re- 

 sembles Hydatina senta and Eosphora 

 Najas ; it is distinguished from the first 

 by its cervical eye, from the latter by the 

 want of frontal eyes. Amongst Lemnae. 

 1-120". 



N. aurita (xxxvi. 3-6). — Described by 

 Mr. Gosse as cylindrical, but frequently 

 pyriform. Head obliquely trimcate, belly 

 nearly straight, posterior extremity pro- 

 duced into a retractile foot (xxxvi. 4 h) 

 with two pomted toes, which organ, 

 being anterior to the cloaca, is not a 

 tail. An oval mark on each side of 

 the head, from which the animal can 

 suddenly project a semiglobular lobe 

 by evolution of the integument (xxxv^. 

 4 a), each lobe fringed with cilia, form- 

 ing a locomotive organ ; fringe of cilia 

 extending across the front of the face 

 as far as the constriction of the neck. 

 Maxillary bulb or gizzard (4 h) large, 

 oval, nearer the ventral than the dorsal 

 side, having imbedded within it a pair 

 of complex jaws (xxxvi. 6 *). A duct 

 leads from the maxillary bulb to the 

 continuation of the alimentary canal, 

 which is wide, subcylindrical, tapering 

 towards the anus, not divided by any 

 constriction, but at once stomach and 

 intestine ; walls thick, probably cellular. 

 Cloaca between the projecting point 

 (xxx\^. 3) and the foot. Ovary large, 

 occuppng the ventral region ; some- 

 times long and clear, containing trans- 

 parent globules (4/), at others gra- 

 nulated (xxx\i. 3), A large developed 

 G,^^ (4 o) often occupying a gi-eat por- 

 tion of the abdominal ca^-ity. Eggs large, 

 covered with short flexible spines. Male 

 unkno-wTi. Water-vascular system con- 

 sisting of two sets of tortuous vessels, 

 commencing at the cloaca (6 «) and 

 terminating at the head, and bearing 

 tremulous tags. Parallel with the oeso- 

 phageal bulb, but nearer the dorsal sur- 

 face, is a large lobulated subglobose 

 mass of dense matter (4 y), white by 

 reflected light, but opaque and hence 

 appearing black by transmitted light, 

 occupying the bottom of a deep cylin- 

 drical sac. A tube runs through the 

 centre of this sac towards the rotary 

 organ, "on which it opens, or at least 

 impinges " (Leydig). As this opaque 

 mass supports the eye-spot, Gosse re- 



