102 THE VICTORIAN NATURALIST. 



usually red, one to four in number, situated on or connected with 

 the brain, and are not to be seen in the adults of some species. 

 The antennas are slender tubes, each bearing a minute brush of 

 very delicate setse. They may be dorsal, ventral, or lateral. 

 The movements and contortions of the Rotifer are effected by a 

 muscular system of several longitudinal and transverse bands — 

 the longitudinal, in some species, stretching from the corona to 

 the toes. The lateral canals, slender tubes running — with many 

 twists and turns — down each side of the body, and usually 

 connected with a contractile vesicle, make up the vascular 

 system. The vesicle — a bladder-like organ — may, in many 

 species, easily be seen contracting and dilating. The precise 

 function of the vascular system is not yet altogether beyond 

 question. Attached to the lateral canals are some very curious 

 little appendages — the vibratile tags. An incessant fluttering 

 movement is maintained within them. Add to these a foot 

 (sometimes, however, wanting) and toes (one, two, or three in 

 number). 



We have yet to mention the distinction of the sexes amongst 

 the Rotifers. It must be observed that the vast majority of 

 those we find are females. In these the ovary is very large, and 

 may contain eggs in all stages of maturity. In some of the 

 commonest genera the male animals are still quite unknown, so 

 that their existence seems problematical. Rotifers produce three 

 kinds of eggs. From the smallest and most rounded the male 

 animals are hatched, and from larger and more oval eggs the 

 females. The real nature and use of the third kind (the 

 ephippial eggs) are perhaps scarcely fully understood at present. 

 Many Rotifers deposit their eggs about the algse. In such cases 

 we frequently observe the developed young animals twisting and 

 turning within the elastic covering of the egg, and exercising 

 their cilia and trophi. 



It may be worth while to note that the open spaces in the 

 bodies of Rotifers are not empty, but contain a perivisceral fluid. 

 It is this fluid which, impelled by muscular contractions into the 

 head and foot, produces the extension of the animal — a process 

 clearly seen in large Floscules. To appreciate rightly the fulness 

 of organization in the Rotifera we must bear in mind that the 

 largest of them are only about yL inch in length, while the 

 smallest measure but z lj> inch. 



The points of cardinal importance for identification of species 

 are the front of the head, cafled the corona, with the attached 

 ciliary wreath ; the eye spots and antennae ; the trophi, of which 

 seven typical forms are described, and the foot and toes, or their 

 absence. With all these, however, allied species have often 

 been confounded by highly expert observers. Should we trip 

 occasionally, therefore, we shall not incur too much blame. The 

 first of the four orders into which the Rotifera have been divided 



