NEW VIEWS OF ANIMAL TRANSFORMATIONS. 633 



of the wall of the body, that vary in number with the species, or some- 

 times with individuals, but are constant for each during the great 

 part of its life. The other is formed of a stomach-like sac, open at 

 bottom, around which are hollow tentacles, which often increase in 

 number with the age of the Polyp (Fig. 10). These tentacles, which 

 are free at their extremities, and united at their bases to form the wall 



Fia. 10.— DiAGRAjaMATic FiGDKE OF Sea-Anemone. 



of the Polyp's body, open inward like the stomachal sac into a great 

 cavity, the circumference of which is divided into cells by the soldered 

 walls of two neighboring tentacles. On the partitions of these cells, 

 and so within the body, the reproductive apparatus is developed ; 

 while in Hydroid Polyps it is generally on the exterior in the form 

 of a bud. This type of structure is much more complex than that of 

 the Hydroid Polyp, which is well represented by the Stylasteridae. In 

 their colonies we find the polymorphism of the Hydroida, and also the 

 nourishers, purveyors, and reproducers. Among the Spinipora^ Spora- 

 dopora, PUohothrius, Errina, these different sorts of individuals are 

 perfectly independent of each other : a simple vascular network dis- 

 tributes among them the food seized by the hunters and elaborated by 

 the nourishers. 



But with the Millipores the nourishers are the most important 

 members of the colony, as they prepare all the nourishment, drawing 

 around them the hunters and reproducers, but without establishing 

 any more intimate relations. With the Astylus, the Stylaster, the 

 Cryptohelia, this movement of concentration around the nourishers be- 

 comes pronounced ; a space forms underneath ; the tentacles, rendered 

 useless by the neighborhood of the hunters, disappear, and nothing 

 remains but a digestive sac around which the hunters perform func- 

 tions exactly like those of the tentacles of a Coralarian Poh^. Each 

 system has now a decided individuality. Another step, and the hunt- 

 ers, from being distinct throughout their whole length, grow together 

 at the base and interlace with the digesters, and the reproducers fol- 

 low in this movement. These different parts are, thenceforward, too 

 near together to require a special vascular system ; the vessels which 

 unite them are simple perforations of their wall which open in the 

 space just below the digesters, and into which the reproducers pene- 



