CTENOPHORA. 15 



Sackchen fehlt". I may also refer to the red glands of Eurhampha-a ■vexilUgera in this connection, 

 though nothing more exactly can be said about their possible homology so long as the structure of 

 the glands in this latter form is unknown. 



The observations on the structure of the ectodermal sacs of Tjalfiella would seem to thro\\' 

 light on the supposed genital ducts in Ctenoplniia described by Willey (Op. cit. p. 329— 331, 

 PI. 21, Figs. 7—9). Though I must agree that the three figures quoted, when combined, show a duct 

 from the genital organ to the exterior, I cannot but express some doubt about the correctness of the 

 observations of Wille\' regarding this point. Ctcrioplana otherwise agrees with Tjalfiella in several 

 important characters and is doubtless nearly related with it. The suggestion then naturally presents 

 itself that the supposed genital ducts of Ctenoplana might be organs homologous to the ectodermal sacs 

 of Tjalfiella (— their greater number in Ctenoplana. 3 to each genital organ, would certainly be no 

 serious objection to the homology with the single organs of Tjalfiella —). It will doubtless also be 

 conceded that, since the highly transformed Tjalfiella has been shown to be in full accordance with 

 the typical Ctenophores in regard to the structure of the genital organs and the way in which the 

 genital products are ejected, it seems very remarkable that the much less transformed Ctenoplana 

 should have acquired a way of ejecting the genital products (or at least the spermatozoa) so radically 

 different from what obtains in all other Ctenophores (— allowing that it remains as yet unknown 

 how the case is in Coeloplana — ). Until renewed researches have been made in the light of the 

 observations here given on the ectodermal sacs of Tjalfiella, it seems to me that the problem about 

 the genital ducts of Ctenoplana cannot be regarded as definitely solved. (Comp. the further remarks 

 on Ctenoplana in Chapter D.). 



The musculature is of the usual Ctenophoran type. The general appearance of the muscles 

 upon the whole very much resembles that of PI. XVII, Fig. 17 in Chun's Monograph. They are 

 arranged in the walls of the chimneys in three main directions, viz. longitudinal, circular and radiating, 

 the latter going directly between the epidermis of the outer and inner side of the chimney; 

 threads are, however, also found, which run in all other directions. In the other parts of the bod\' the 

 arrangement of the musculature is essentially the same. It is worth pointing out that there is no special 

 arrangement of the muscles in the basal part, adapted to perform creeping movements of the animal. 



The threads are branched at their ends in the usual way, though not to a very extensive degree. 

 They are very fine, measuring only ca. 0001— 0-003""". ^ ^^^^ "°^ observed with certainty any anastomoses 

 between the muscles. The finer histological structure of the muscles I have not been able to investi- 

 gate in a satisfactory way on the material available. — Between the muscles are found some other 

 histological elements, viz. amseboid-looking cells with pseudopod-like prolongations, corresponding to 

 those described and figured by Chun (Ctenoph. d. Golfes v. Neapel. Taf. XVII, Fig. 17 -19); more 

 numerous are some peculiar small aggregates of cells in linear or more irregular arrangement (PI. VIII, 

 Fig. 9). They are sometimes running out into muscle-like prolongations, sometimes without such 

 prolongations. I suppose that they represent development stages of muscles, corresponding to those 

 described and figured by vSamassa in Error (Zur Histologic d. Ctenophoren, p. 212— 214, Tab. XI, 



Fi,g. 58)- 



To enter on a discussion of the nervous system, one of the most difficult problems in Cteno- 



