POLYZOA. 525 



No. 97). It is always regarded as one of the most exqui- 

 site specimens of the class Polyzoa ; should there be 

 any difficulty in finding the animal itself, the eggs, met 

 with late in the summer or autumn, should be care- 

 fully stored in an aquarium without fish. The eggs or 

 " statoblasts," No. 95, are small, dark, circular bodies, 

 about the size of a pin's bead, surrounded by a series of 

 minute hooked spines ; the animal conceals them among 

 tangled masses of decayed grasses and confervas. Polyzoa 

 are known to live upon Desmids and Alga3 ; and to keep 

 them alive the tank must be freely supplied with such 

 kinds of food. Cristatella Mucedo is rarely found in the 

 same spot a second day, it wanders about apparently in 

 search of food ; it is, therefore, provided with a contractile 

 disc or foot, and by means of this it creeps about not far 

 from the surface of the water, for it delights to display its 

 beautiful crests of tantacula (about eight in number), in the 

 broad light of day or sunlight ; in this respect Cristatella also 

 differs from most Polyzoa. Below the external margin is 

 a series of tubular chambers visible through the translucent 

 membrane ; and the csensecium or common dermal system 

 is of a light yellow colour, often concealing several dark, 

 brownish-looking eggs. 



Lophopus crystallinus is a finer Polyzoon than the former, 

 and displays beautiful plumes of transparent tentacles 

 arranged in a double horseshoe-shaped series. They at 

 times abound in slow running streams, adhering to the 

 stems of water-plants. "VY hen first removed from the water 

 thev resemble masses of the ova of one of the water snails, 

 and have often been mistaken for them. On putting one 

 of those jelly-like masses into a glass trough with some of 

 the clear water from the stream, delicate tubes will be 

 cautiously protruded, and then the beautiful fringes of cilia 

 are soon brought into play. The organization of L. Crys- 

 tallinus is simple, although it is provided with organs 

 of digestion, circulation, respiration, and generation. A 

 nervous 1 and muscular system are also tolerably well 



(1) It has been demonstrated by Fritz Miiller that the Polyzoa possess a ner- 

 vous system : — "The nervous system of each branch consisting of — 1st, a consi- 

 derable sized ganglion situated at its origin ; 2d, of a nervous trunk running the 

 entire length of the branch, at the upper part of which it subdivides into 

 branches, going to the ganglia of the internodes arising at this part ; and 3d, of 



