70 GENERAL HISTORY OF 



commencement of the oesophagus, consists of a hard 

 bulb, somewhat resembhng the gizzard of birds; it is 

 composed of two parts, the inner surface of each being, 

 in 48 genera, furnished with teeth, which, by pressure, 

 can be detached. Their number and arrangement form 

 excellent characters for the systematist, and therefore I have 

 introduced figures of them, with the oesophagal bulb, to 

 illustrate several of the genera possessing them. This 

 bulb, it is worthy of notice, is the first part of the young 

 that is visible within the egg. Beneath this bulb, and 

 attached to the oesophagus, or upper part of the stomach, 

 is a pair of glands, usually of an oval form, sometimes, 

 though rarely, cylindrical, or forked ; these are considered as 

 the pancreas. In some genera, gall ducts are also seen 

 (Enteroplea) . The stomach in some genera (Notommata) 

 is furnished with biliary glands. 



Section XXXI. — The Reproductive System. 



This, in most respects, resembles that of birds, but both 

 sexes are united in the same individual. They deposit 

 only a few eggs at a time. The size of the egg is about 

 l-36th that of the parent, and the young of those in which 

 incubation is completed before expulsion is sometimes 

 two -thirds. 



Although the Rotatorial Infusoria are not endowed with 

 the various faculties of reproduction possessed by the 

 Polygastrica, yet their vast increase by eggs only would 

 astonish most persons who have not considered this 

 subject. Dr. Ehrenberg informs us that he insulated a 



