294 



Characteristics of Rotifers. 



"mouth.. In this genus great voracity is exhibited, as may be 

 imagined, from the quantity of other rotifers and objects of 

 various kinds often seen in the stomach at the same time. 

 The body of the Asjplanehna and its iuteguments are very 

 transparent, and the stomach, usually yellow or brown, so that 

 the little creatures are easily seen in a bottleful of water lucky 

 enough to contain them. They afford excellent illustrations of 

 ciliary stomach-currents. The whole stomach, appears lined 

 with cilia, and they produce, by a somewhat violent action, 

 remarkable whirlpools amongst the particles of food. Cono- 

 chilus will show the same thing in a less striking way. It is 

 not so voracious, the cilia are more delicate, and the stomach, 

 not so filled with hard matters capable of turning the currents 

 out of their path. Powers of at least 600 or 700 are neces- 

 sary to see these phenomena well, and they require careful 

 illumination. The ciliary currents in the stomach in Asplan- 

 chna are shown in the plate. The stomach-currents are plain 



in many of the Brachions, and 

 their existence may be demon- 

 strated with powers of about 

 200 to 250. 



From the digestive appa- 

 ratus we may proceed to the 

 water-vascular system, which 

 is probably, as before stated, 

 respiratory and excretory. It 

 consists of delicate bands or 

 tubes, to which, in most cases, 



" vibrating tags" are attached. 



This 



system of apparatus is 

 connected with, the contrac- 

 tile vesicle popularly called a 

 " heart," though no physiolo- 



be an 

 of blood circulation. 

 The annexed diagram shows 

 the water-vascular system of 

 Not<> \a aurita, as repre- 



sented by Mr. Gosse ("Trans. 

 Mic. Soc.," 1850). The sto- 

 mach and other organs are not 

 shown in this drawing. In 

 Asjplanehna I have noticed the tags, as shown in the accom- 

 panying plate, Fig. 5. They were ciliated at their ends, 

 and exhibited a flickering motion in the direction of the dark 

 line ; and this was probably occasioned by an internal cilium 

 like that which Prof. Huxley describes in Lacinularia. 



gist now considers it to 

 organ 



Fig. 5. — The Water Vascular System 

 of Notommata aurita, showing the twisted 

 tubes, ribratile tags, and contractile \ eair 

 cle. Reduced from drawing by Mr. 

 Gosse. Viscera omitted. 



