i6 



CTENOPHORA. 



phores, would not be appropriate on the basis of the material available. This question can only be 

 discussed appropriately, when material treated lege artis is at hand. It must however be pointed out 

 that no indications of the existence of distinct ganglia, as are described by Abbott in Coeloplana 

 (Op. cit. p. 6i, Fig. B) were found. 



B. Development; Anatomy of the Cydippid-stage. 



When ripe the eggs fall into the cavity of the genital organ, from which they must be trans- 

 ferred through the main vessel to the ramifying canals and then transported in some way or other to 

 the place, where they are going to hatch. Though no direct observations have been made as to this, 

 it cannot be doubted that it must happen along this way. How the transport is made, remains un- 

 certain, but it may be suggested tliat the eggs wander by active amseboid movements, since cilia have 

 not been found within the gastrovascular canals. To be sure, it can scarcely be taken as definitely 

 proved that cilia do not occur in the gastrovascular canals, the histological preservation being insuffi- 

 cient for proving the non-existence of cilia in some places; but the fact that they are are easily observed 

 in other places (e. g. in the pharynx and in the chimneys) makes it ver}- probable that they really do 

 not exist in the gastrovascular canals; this supposition also gets an important support from the fact 

 that cilia are not found in the gastrovascular canals of Coeloplana (Abbott; op. cit. p. 54). (In typical 

 Ctenophores the low epithelium in the gastrovascular canals is ciliated, while the high cells of the 

 ridges carry no cilia). That the eggs wander through active movements is the more probable, since 

 in other Ctenophores direct movements of the eggs have ben observed both by Kowalewsk}', 

 Agassiz and Chun, the latter author giving the following description of the movements as observed 

 in Eucharis, Lampetia and Cesttis (Monogr. p. 100) "... Bewegungen . . . , welche, darin bestehen, dass das 

 Ektoplasma sich contrahirt, bald an dieser, bald an jener Stelle der Peripherie sich in grosserer Menge 

 ansammelt uud das Endoplasma hin- und herpresst. Es fehlte nur noch, dass die verdichteten 

 Stellen der Peripherie sich zu Pseudopodien ausziehen, um die Ahnlichkeit mit einer amobenartigen 

 Bewegung zu vervollstandigen". Through such movements it may be understood that the eggs can 

 wander from the genital organs to the brood-cavities. 



The fertilisation must take place within the gastrovascular canals, the eggs evidently not 

 leaving the animal. Since the spermatozoa are also found in quantities in the canal system, both eggs 

 and spermatozoa developing contemporaneoush- in the same genital organ, as appears from the sec- 

 tions, it seems hard to see how self-fertilisation can be avoided. Another thing is that it cannot be 

 doubtful that foreign spermatozoa may have access to the eggs. I have observed spermatozoa within 

 the excretory canals, which proves that they are liberated this way (perhaps also through the mouth 

 and the chinmeys); the foreign spermatozoa probably must enter through the chimneys and the mouth, 

 perhaps also through the excretory canals. 



Tlic brood-cavities in which the development of the embryos takes place are probably 

 situated in the end branches of the ramifying gastrovascular canals. I ha\e,' however, been unable to 

 prove tliis definitely on the sections; but the canals are seen to abut against the brood-chambers, 

 not continuing beyond them, so I feel rather convinced that such is the case. Further observations 



