2l6 ROTIFERA 



are so close together that the pigment-cups have the shape of an 

 x, or else they are seated in the dorsal region of the head behind 

 the disc. In some cases they lie just under the ciliary wreath, 

 or even within the region of the disc, and pass towards its ventral 

 side in Pedalion (Fig. 117, A, e). In Rotifer they lie just under 

 the dorsal side of the proboscis just below its apex. The median 

 and two lateral eyes often exist together, as in Eosphora ; and 

 sometimes additional paired eyes exist. In Furcidaria longiseta, 

 var. grandis a pair of pigment spots (eyes ?) occurs at the hinder 

 end of the body just in front of the foot. 



The active Ploima show a spontaneity of movement and 

 marked power of avoiding obstacles, etc. This is still more 

 marked in the very active Pedalion, which, as Rousselet notes, 

 clearly avoids capture by the dropping tube, aided by its sense 

 of sight, as he suggests, or by the tactile or olfactory powers of 

 the antennae. They must rank as psychically high in the scale 

 of creatures of simple organisation. 



Reproductive Organs and Reproduction. The most con- 

 spicuoiis organ in the female is the large yolk-gland or vitellarium 

 (Figs. 106 and 109, A, vni), which was regarded as the ovary by 

 all the older observers. It consists usually of eight cells, with 

 conspicuous nuclei, lying on the ventral side of the stomach, and 

 frequently displaced to one side ; but in most Asplanchnidae it 

 forms a broad transverse band of numerous cells. In Pterodina 

 it is horseshoe-shaped, while in Seisonaceae and Bdelloida it is 

 paired, either gland containing four or eight cells. The true 

 ovary or germarium (Fig. 106, gm) lies more or less hidden 

 between the yolk -gland and the stomach ; it is composed of 

 numerous minute rounded cells, of which the hindmost for the 

 time being enlarges by nutrition from the yolk-gland, and finally 

 receives a membranous shell. This true ovary is somewhat 

 lateral in most Eotifers, but is median in Asplanchnidae, and 

 paired in Pterodina, Bdelloida, and Seisonaceae. A membranous 

 covering is common to the ovary and yolk-gland (paired when 

 these are paired) ; it is continued into a thin-walled tube or 

 oviduct, which opens into the cloaca on its ventral side beyond 

 the bladder or common renal duct. In the viviparous species 

 the mature ovum (Fig. 112, CHI) usually lies in the oviduct, 

 dilating it into a sort of " uterus " until the birth of the young. 

 The ordinary eggs or 



