326 



ZOOLOGY 



The excretory system consists of paired nepliridicd tubes 

 (Figs. 264 and 267, nph.) resembling those of the Platyhelminthes. 

 Their general direction is longitudinal, but they are a good deal 

 coiled and give off little tag-like processes ending in flame-cells. 

 With the end of each tag, projecting into the body-cavity, is a long 

 flagellum. The lumen of the tubes is intra- cellular : it is uncertain 

 whether or not the cavities of the flame-cells communicate with the 

 body-cavity by apertures in their walls. Posteriorly the nephridial 

 tubes open into a bladder or contractile vesicle (c. v.), the contents 

 of which are discharged, by periodical contractions, into the 

 cloaca. 



Nervous System and Sense Organs. — There is a single 

 ganglion or brain (Figs. 264 and 267, br.), of proportionally large 



Fig. 266.— Brachionus rubens. A, male ; B, female, with attached eggs ; c. gl. cement- 

 glands ; cv, contractile vesicle ; n^h. nephridial -tube ; ov. ovum in body ; ovl. ova attached 

 to base of tail ; p. penis ; t. tail ; is. testis. (After Hudson and Gosse.) 



size, situated at the anterior end of the body, above (dorsal to) the 

 mouth and pharynx. On the dorsal surface of the brain, where it 

 comes into contact with the body-wall, is a small red eye-spot (e.). 

 The only other organs which can be considered as sensory are 

 three structures known as tactile rods or feelers ; one of these (d.f.) 

 is a small cylindrical process tipped with stiff hair-like bodies, 

 which projects from the dorsal surface just behind the trochal disc : 

 the other two (l.f.) are paired, situated on the dorsal surface of 

 the lorica and not prominent. 



The tail contains a pair of cement glands {c. gl.), by the secretion 

 of which the animal is able temporarilj' to attach itself. 



Reproduction and Development. — The sexes are lodged 

 in distinct individuals, which present a striking degree of sexual 

 dimorphism. The preceding description applies to the female. 



