22 



ZOOPHYTES. 



into the stomach. It appears then that this is the means by which 

 the results of digestion, or the nutrient juices, are distributed through 

 the zoophyte; and that the sides of the visceral cavity have through- 

 out the power of appropriating these chyloid fluids, thus kept in cir- 

 culation. There appears to be no system of circulation independent 

 of this chyle distribution. 



In certain filiform species (the Tubularia3, fig. 1), Lister distin- 

 guished a similar motion in the pulpy fluids of the axis, except that, 

 instead of vibrating, it was circulatory, part of the fluids moving up 

 and part descending by a simultaneous action. They often passed 

 into the stomach, and were continuous in their motions with the 

 movements of this organ. It appears therefore that the tubular axis 

 of these species corresponds with the visceral cavity in the higher 

 zoophytes. 



The visceral cavity in the Hydroidea differs widely from the same 

 in the Actinoidea, in the absence of vertical fleshy lamellae around 

 the sides. Rudiments of these lamellae appear however to have been 

 detected by Lister in a Tubularia. It is due to this simplicity of 

 structure that the Hydra will live and eat when turned inside out. 



The food of these animals consists of minute animalcules or worms, 

 or whatever of animal life is sufficiently small to become their prey. 

 The prey is secured usually by means of the tentacles, which entwine 

 around it, or together enclose it, and convey it to the mouth. 



14. Reproduction takes place either (1) by ovules proceeding out 

 from the sides of the polyps ; (2) by lateral buds developing young, 

 which, on arriving at maturity, separate from the parent; (3) by 

 lateral buds which are persistent; (4) by artificial sections. 



The ovules appear either single or in naked branched clusters ; or, 

 clustered and enveloped within a common receptacle or ovarian 

 vesicle. The figure heading this chapter (\b) represents a branched 

 cluster as they sometimes appear in the Tubularise. Single ovules 

 also are presented by many species of this family : they characterize 

 moreover the Hydra. 



The ovarian vesicles, in which a number of ovules are enclosed 

 under a common envelope, belong to the Sertularia and Campanu- 

 laria families. Some of these vesicles are represented in the following 

 figures, and others in figure 2, or enlarged in figure 5. They gra- 

 dually develope from the side of a branch, or at times from a creeping 

 root-like shoot, which grows outward, like the creeper of a plant, 

 sending up its buds and flowers at intervals (fig. 8). The ovules 



