248 



NATURAL HISTORY. 



JAWS OF BRACHIONUS BKEVISSIMUS. 

 (After Ehrenberg.) 



genus (Pompholyx) thus gifted has no foot, whilst the genus Pterodina has a disc on its foot, and 

 is a very globose-looking form, and it carries its eggs for a time. 



In the last genus to be noticed of this family (Noteus) there are no eyes, and the foot is forked, 

 and the body has spines in front and behind, being usually large, or from T yth to y\yth of an inch. 



Amongst the Rotifera, with the trochal discs or rotary organs divided, are some in which the 

 division is greater than in the two families just noticed. In the family Hyclatina and that of 

 Euchlanidotse the wheels are many-parted, and the first have no lorica, whilst in the latter the 

 shell is very well developed, and has curious appendages, such as setae in the genera Euchlanis 



and Stephanops, hooks in Colurus, horns in Salpinus. There 

 are spears or respiratory tubes in Euchlanis, and a helmet in 

 Stephanops. In the genus Monostyla the foot is a sharp style, and 

 in Mastigocerca the foot is as long as the body, or yV of an inch, and 

 the lorica is prismatic. The genus Squamella has four eyes. The 

 species of this genus carry their eggs attached to the outside of the 

 body. 



In many of the family the muscular fibres by which the shape 

 of the body is changed are very visible. The nutritive organs are 

 very obvious, and the intestine is simple and conical, with or without the part which represents 

 a stomach. The water system, with its tremulous napping of minute cilia within the tubes, is 

 visible, and in most the nervous system is to be seen. There are no crushers or inastax in the 

 genus Enteroplea ; it has no eyes, and it is thus a very simple Rotifer, and segmentation in any 

 degree barely exists, the small foot being forked. In Hydatina, another genus, there are no eyes, 

 two jaws, and they are divided to show numerous teeth. Hydatina senta was the Rotifer which 

 Ehrenberg especially studied, and it is common and very transparent. Its species are not very small, 

 or 2"mth of an inch long. 



Of the family Hydatinea, in which there is not an investing lorica, and the rotary organ is 

 multiple, there are no less than eighteen genera, and they are characterised by the absence or number 

 of eyes, the position of these organs, the nature of the foot and appendages to the body. There are 

 several distinct rows or circles of cilia, which are distinctly separated from each other, forming the 

 multiple wheel or rotary organs. Except in the genus Polyarthra, 

 which has no foot, all the other genera have a long pincer-like process 

 resembling a tail, and this genus is characterised by a single eye on 

 the neck, and by the presence of six cirri or fin-like processes on 

 each side of the body. 



The species of the genus Notommata are sometimes parasitic, 

 and undergo some degradation of form, and Notommata tardigrada 

 has the rotary organ greatly diminished. Two species live within 

 the beautiful microscopic alga, called Volvox globator, and another 

 in the vesicles of a Vaucheria. The well-formed species have a 

 single eye and a forked tail. 



Notommata lonyiseta has two setae in the position of the tail, 

 and several times longer than the body. 



The Triarthrae have two eyes, and Triarthra longiseta has a tail, or foot, three times as long as 

 the body, and very long cirri also. It moves in a jerking manner, and is ^-jy^th of an inch in length. 

 It carries its ova attached to its sides, and may exist in such multitudes as to colour the water a 

 milky white. Gosse has described Asplanchna brightwelli and A. ,riodonta. The females have 

 jaws with a single tooth and a single eye-spot, and they are without feet and the end of the intestine. 

 The males have neither jaws, pharnyx, nor stomach. 



The family Floscularidse contains some very beautiful forms of Rotifers, but they are very 

 aberrant from the group as a whole. The body is elongate, and the tail or foot is long, more or 

 less imperfectly segmented and fixed. They are for the most part protected by a tube made up 

 of a gelatinous excretion of the body, and extraneous substances or pellets of their excrement. 

 The rotary organ is much modified, and is partly encased in some and is lobed in others, whilst in 



POLYAKTHRA FLATYPTEK. 



