DEVELOPMENT OE THE CTENOPSOEA. 103 



bulging o£ this membrane ; while the funnel and tlie vessels 

 wbicli proceed from it are formed out of the large-celled endo- 

 dermal tissue. This view, which is quite in accordance with 

 my own observations (see above, p. 91), is inconsistent with the 

 opinion that the large clear central cells serve only as a food-yolk. 

 The further, or post-embryonal development of the Cteuophora 

 — that which takes place after their exit from the egg — does not 

 offer the same uniformity as that found in the stages hitherto 

 traced ; and Chun describes it as it presents itself in different 

 groups. He takes MucJiaris muUicornis, which had already 

 afforded him a type for his description o£ the earlier stages of 

 Ctenophoral development, as a type also of the post-embryonal 

 development of the lobed Ctenophora. 



When Eucharis mtiUicornis leaves the egg it is of a pyriform 

 figure and laterally compressed, so that the axis in the plane of 

 the funnel exceeds in length the axis in the plane of the stomach. 

 This is the characteristic condition of the achdt state of another 

 Ctenophoral genus, Mertensia, and is in striking contrast with the 

 adult form of Eucliaris, in which the axis in the stomach-plane 

 is longer than that in the funnel-plane. 



The tentacular apparatus lies concealed in small sheath-like 

 depressions of the surface, one on either side. Each sheath con- 

 tains two short rudimentary tentacles, of which the upper one 

 rapidly grows and develops lateral branches, while the lower one 

 remains rudimentary. The central nervous system is surrounded 

 and overtopped by four roundish prominences of the gelatinous 

 tissue. The ribs consist each of from four to five swimming- 

 plates. The cells which had migrated into the jelly from the 

 ectoderm and stomach-walls have already become elongated into 

 true muscle-cells, and show themselves as fibres lying between 

 the gastrovascular apparatus and the periphery. 



Hitherto the vascular system has not shown an obvious dis- 

 tinction into funnel, central, and peripheral portions, and consists 

 merely of two sacs which communicate with the central lacuna 

 and send out short bulgings towards the ribs and the tentacular 

 apparatus. The next changes, however, are essentially marked 

 by the increased differentiation of the vascular system. Chun 

 describes the two vessels which run along the broad side of the 

 stomach towards the mouth (Magengefiisse) as originating in 

 ampuliform outbulgings of the two endodermal sacs ; and though 



