COMPOSITE ANIMALS. 103 



eye. There is one form i.e., Cristatella mucedo 

 which is exceptional. It loves the light, and floats 

 about sometimes unattached on the surface of the 

 water, and at others creeps about on the plants. 

 Hence it is generally called the Travelling Poly/oon. 

 It does not travel fast, however, and its method of 

 locomotion is involved in some obscurity; but as 

 the under-side consists of a contractile disc, it is 

 probably by means of its contraction and expansion 

 that it gets along. 



The fresh -water forms comprise only a small por- 

 tion of the great class of animals designated Polyzoa, 

 which are mostly marine ; but enough has been said 

 to show that we have in our ponds and canals 

 a beautiful and intensely interesting variety of this 

 wonderful form of animal life ; and moreover, they 

 will bear domestication, so that one may keep up 

 a stock of almost every variety in a few glass 

 jars. Even thus seen with ordinary vision in 

 clear water, with aquatic plants, they are very 

 beautiful ; and when required they will lend them- 

 selves without injury to gentle separation with a pair 

 of fine scissors, for our more exquisite pleasure 

 and instruction under the microscope. 



