IV 



VERMESS Y STEM A TIC RE VIE W 



185 



Sub-Order 1. Testicardines. 



The shell valves are hinged together by interlocking processes. An anus is want- 

 ing. Tcrclrutula, Waldhcimia, Thccidium (attached by the larger shell valve). 

 Argiope, Ehynconella (Fig. 125, p. 191), Spirifcr. 



Sub-Order 2. Ecardines. 

 Without hinge. Intestine with anus. Crania, Lingula. 



CLASS V. Eotatoria (Wheel Animalcule, Fig. 123 ; Fig. 161, p. 245). 



Small, mostly microscopic animals. Inner segmentation wanting. At the 

 anterior end a variously shaped ciliated organ (wheel organ) ; posterior end prolonged 

 in a frequently segmented appendage (foot-stalk). Cloacal aperture dorsal on the 

 boundary of body and foot. A vascular system 

 wanting. One pair of nephridia, of the embryonic 

 type, with several inner ciliated cells, emerge with 

 the anus and the oviduct into the cloaca. Sexes 

 separate. The males small, with degenerated ali- 

 mentary canal. Chiefly fresh-water animals. Forms 

 living in attached tubes or envelopes: Floscularia, 

 Stephanoceros, Melicerta, Lacenularia. In these the 

 wheel organ is produced into lobes or tentacles. 

 Free-living forms : Notommata, Hydatina (Fig. 161, 

 p. 245), Brachionus (carapaced), Asplanchfi, Seison 

 (parasitic on Nebalia). 



We must place near the Rotatoria. the peculiar 

 species DinopMlus (Fig. 162, p. 246), which has the 

 same appearance as certain annelid larvse. Male 

 and female are alike, or the male is smaller, with- 

 out intestine. The whole ventral side of the body 

 is ciliated. Besides this there are several ciliated 

 rings lying one behind the other on the body. A 

 wheel organ is wanting. Nephridia in segmental 

 arrangement of the embryonic type. 



fid 



CLASS VI. Chzetognatha (Fig. 152, p. 227). 



Body cylindrical, elongated, with horizontal 

 border of fins (lateral fins, caudal fin) round the 



Appendage to the Race of Vermes. 



FIG. 123. Diagrammatic repre- 

 sentation of the organisation of a 

 Rotifer, from the side, ro, Wheel 

 organ ; g, brain ; a, eye ; pli, pharynx; 

 in, stomach ; n, nephridium ; md, 

 gastric gland ; g, genital gland ; 1:1, 

 posterior body. Head tolerably distinctly separated cloaca ; M, cement gland of the 

 from the trunk. Body cavity spacious ; divided by foot (/). 

 partition walls into three consecutive parts head 



cavity, trunk cavity, and tail cavity. Mouth surrounded by seta? (jaws). Intestine 

 straight, anus ventral, at the commencement of the tail. The central nervous 

 system consists of the brain, the cesophageal commissures, and a large ventral ganglion 

 lying in the trunk. Without vascular system. Hermaphrodites ovaria in the trunk 

 cavity, testes in the caudal cavity. Paired efferent ducts (transformed nephridia ?) 

 emerge to the right and left at the end of the trunk and of the tail. Live in 

 the sea. Sagitta, Spadella. 



