TABELLARIA. 



[ 627 ] 



TiENIA. 



contents of the filaments next ascend and 

 accumulate in the peridiole, at length form- 

 ing a black globule (sporange?). While this 

 is ripening, the apices grow out into long 

 simple filaments. 



BiBL. Ehrenb. Verhandl. Naturf. Freund. 

 Berlin, i. p. 91; Fries, Syst, Myc. iii. p. 329; 

 Berkeley, Ann. Nat. Hist. i. p. 257. 



T. 



TABELLARIA, Ehr.— A genus of Diato- 

 maceae. 



Char. Frustules tabular, attached, at 

 first united into a filament, subsequently 

 cohering only by the angles, with longitudi- 

 nal vittse interrupted in the middle ; valves 

 inflated in the middle and at each end. 

 Aquatic. 



T.flocculosa (PL 13. fig. 27 a, b). Vitt« 

 alternate, middle and ends of the valves 

 equally inflated. Length 1-960 to 1-840". 



T. ventricosa. Vittse alternate, median 

 inflation the largest. Length 1-960". 



T. fenestrata. Frustules oblong; vitta3 

 opposite ; inflations equal. Length 1-600 

 to 1-290", 



Five fossil species. 



BiBL. JLiitzmg, Sp. Alg. MS. 



TABLE. — A table for the conversion of 

 foreign into English measures, is given un- 

 der Measurement (p. 418). 



TADPOLE. See Frog (p. 273). 



TiENIA (Tape-worm).— A genus of En- 

 tozoa, belonging to the order Cestoidea. 



Char. Body elongate, compressed, jointed. 

 Head mostly broader than the neck, with 

 four suctorial depressions; and usually a 

 median, imperforate, retractile rostellum, 

 very frequently armed with one or two cu'- 

 cles of minute recurved hooks, especially in 

 the young state. Genital orifices situated at 

 the margins of the joints, either on one side 

 only, or on both margins and on alternate 

 joints. 



The TcBnice, of which the common tape- 

 worm may be taken as the type, are found 

 in vertebrate animals alone, and in these 

 only in the alimentary canal. They are most 

 common in birds, next in mammalia, then 

 in fishes, and lastly in reptiles. 



The species are very numerous ; Rudolphi 

 enumerates 146, of which 53 were considered 

 doubtful. Dujardin admits 135 species. 



Tcsnia solium, the common human English 

 species, varies in breadth from 1-50 to 1-40" 

 at the anterior part, to about 1-3" at the 



middle and posterior part. At the anterior 

 extremity is situated a central rostellum, 

 which is surrounded by a crown of small 

 recurved hooks, as in PI. 16. figs. 1 /& 10. 

 Behind these are four suctorial depressions, 

 which are not pervious at the bottom. The 

 digestive system, according to Blanchard, is 

 represented by two tubes or lateral canals 

 (PL 16. fig. 14 6), having between them a 

 transverse canal at the summit of each joint. 

 These extend from the anterior to the pos- 

 terior end of the body. In the cephalic 

 portion, directly behind the suckers, there is 

 a kind of lacuna or furrow communicating 

 directly with these intestinal tubes ; and it 

 appears that the nutritive matters respired 

 by means of the suckers penetrate into this 

 lacuna, and thence into the digestive canals. 

 These tubes have distinct walls, and are best 

 seen when the animal has been macerated in 

 water, and is examined by transmitted light, 

 or after having been injected. 



The vascular system, according to the 

 above author, consists of four longitudinal 

 vessels (PI. 16. fig. 14 h) situated a little 

 above the intestinal tubes, and infinitely 

 more slender than these. They traverse the 

 whole length of the body, and between them 

 are numerous transverse vessels (PI. 16. 

 fig. 14). 



The male generative organ consists of a 

 slender coiled tube, extending to near the 

 principal ovigerous canal, where it is pre- 

 ceded by some very small testicular capsules 

 (PL 16. fig. 14 c). The slender tube termi- 

 nates in a duct (PL 16. fig. 14 c?), which 

 opens into the lateral orifice, or sometimes it 

 projects externally in the form of a spiculum. 

 The ovary consists of a principal median 

 canal, presenting slight flexuosities, and ex- 

 tending nearly from one end to the other of 

 each joint. It presents csecal branches on 

 both sides, and opens by a slender oviduct 

 (PL 16. fig. 14 e) just within the genital 

 orifice. 



The ova are innumerable ; one is figured 

 in PL 16. fig. 15. They consist of an outer 

 delicate membrane enclosing a gelatinous 

 substance containing numerous highly re- 

 fractive globules. Within this is another 

 very delicate and transparent membrane, 

 closely applied upon a brittle, dark-looking 

 (by transmitted light, but white by reflected 

 light), thick envelope, within which is 

 the yolk or embryo, according to the 

 state of development of the ovum. Very 

 frequently the hooks of the young taenia 

 are seen imbedded in its centre, as shown in 



2s2 



