DEVELOPMENT OE TUE CTENOPKOEA, 105 



the animal corresponding to that of the adult ; for we have tlie 

 stomach-axis now exceeding in length the funnel-axis. 



A further remarkable fact has been noted by Chun in this 

 medusa-like larva, uamelj the total disappeai'auce of the tentacle 

 and the atrophy of the vessel which had supplied it ; while at a 

 later stage an entirely new tentacular apparatus becomes deve- 

 loped, and remains as the definitive tentacular apparatus of the 

 EucTiavis. 



Tlie central nervous system lies quite free on the aboral pole. 

 Within the bell-like capsule may be seen the heap of otolites 

 borne by the four large curved cilia, in which the lines of minute 

 cilia which run along the course of the nerves terminate. The 

 pole-plates have acquired their elliptical form ; and on the sides 

 of these the funnel-canals open with wide excretory orifices. 

 The eight nerves run each to a swimming-plate series, extending 

 througli the entire length of the series, and communicating with 

 every swimming-plate. At some distance from the last plates of 

 the subtentacular ribs may be seen a number of minute plates, 

 which are kept in connexion with the subtentacular ribs by a line 

 of cilia. In these four rather isolated series of minute swimming- 

 plates we see the foundation of the four so-called auricles, which, 

 along with the lobes, are characteristic of the lobate section of 

 the Ctenophora. The continuation of the nerve which runs 

 along the rib may be also followed along the rudimentary 

 auricles. 



In the later stages the body becomes much elongated in the 

 direction of the main axis, and the four gelatinous prominences 

 become developed on the aboral pole round the central nervous 

 system. At the same time the anastomosing meridional vessels 

 have become thrown into complicated windings on the lobes, and 

 the two stomach-vessels finally enter into the anastomosis. 



A peculiarity of structure, which seems to have escaped the 

 earlier observers, has been noticed by Chun in Eucharis. This 

 consists in a blind sac, which, in the young animal, begins to 

 show itself over the tentacle-basis in each body-half It thence 

 extends obliquely towards the stomach ; and when arrived in the 

 proximity of the stomacli, it extends with the further growth of 

 the animal in a direction chiefly towards the sense-pole and 

 parallel to the stomach-walls, until in fully developed animals it 

 reaches the funnel, or may even extend beyond it. Cliun is 

 unable to throw any light on the morphological significance or 



LINN. JOUEN. — ZOOLOGY, VOL. XVI. 8 



