EMBEYOLOGY OF CAMPANULARIA GELATINOSA. 103 



tog-ether into a mass, from which all the nutritive part appears to have 

 been extracted. This constitutes the meconium. 



(262.) In some instances, the nutritious fluid that circulates in the 

 interior of the parent polypary may be seen to penetrate as far as the 

 interior of the vitelline cavity of the embryo, which thus seems to 

 derive its nourishment at the expense of the general community ; and 

 when it is taken into consideration that the ova are formed in the 

 common fleshy substance lining the walls of the ovarian vesicle, and 

 that the nutritious fluid is diifused throughout its entire mass, it is easy 

 to understand how, after the (external membrane surrounding the em- 

 bryo is ruptured, it is enabled to penetrate, by means of the mouth, 

 into the interior of its stomachal cavity. 



(263.) Mention has been made, in the above description ( 256), of 

 cells which give origin to organs of sensation, and which make their 

 appearance at a very early period. These present the same appearance 

 as the eyes and the ears of the lower mollusca and other inferior ani- 

 mals, and moreover present a similar organization, being composed of 

 two spherical vesicles enclosed one within the other. That the young 

 polyp possesses these organs of relation with the external world is 

 undeniable, although no traces of them remain when the animal has 

 acquired its full development ; but what is still more surprising, accord- 

 ing to the researches of Van Beneden, coexistent with these instruments 

 of sense, there are perceptible a muscular system and an apparatus of 

 nerves and nervous ganglia which, like the preceding, are only of a tem- 

 porary character. While the young polyp is still enclosed in its cell, two 

 bands, apparently composed of muscular fibre (fig. 48, P, d), make their 

 appearance ; these run from one margin of the disk to the opposite 

 edge, crossing each other at right angles, in the centre, so as to present 

 a cruciform arrangement. These bands are quite isolated, and their 

 muscular fibres distinct and transparent. By their action the margins 

 of the disk are approximated, enabling these little animals to imitate 

 the movements so characteristic of the Medusae. 



(264.) Situated upon the course of the bands above described, close 

 to the edge of the vitelline sac, are little rounded bodies (fig. 48, p, e e), 

 presenting an irregular and slightly tuberculated surface, considered by 

 Van Beneden to be nervous ganglia. These little bodies are four in 

 number. No filaments of intercommunication or nervous cords have as 

 yet been detected even proceeding to the organs of sensation, but the 

 ganglia seem to be adherent to the muscular bands apparently by the 

 intermedium of nerves. 



(265.) It may appear a little rash, says the eminent observer to 

 whom science is so much indebted for these researches, to speak of 

 muscles, nerves, and organs of sensation in the embryo of a polyp, 

 which at a later period presents no traces of the existence of such ap- 

 paratus ; nevertheless the polyp, during its free state, must necessarily 



