32 



CTENOPHORA. 



It is thus seen that the genera Tjalfiella, Ctenoplaiia and Coeloplana agree in several important 

 characters: the numerons folds of the pharyngeal cavity, the branching peripheral canals and 

 the lacking of the meridional canals of the gastrovascular system, the unbranched excretory 

 canals and (probably) the single genital organs. All these characters distinguish them sharply from 

 all the rest of the Ctenophores. The rudimentary character or total loss of the costa; might not a 

 priori be taken as a proof of the near relation between these forms, as it is evidently an adaptive 

 character; but since it is in accordance with the other characters, it tends to accentuate the near 

 relation between the three forms. 



Much more different from Tjalfiella are the two other forms made known recently as trans- 

 formed Ctenophores, viz. Dogielia malayana Pedaschenko and Hydroctciia Salenskii Dawydoff. It will be 

 desirable to give some remarks on these two forms also on the present occasion, in order to show 

 whether they have possibly any relation to Tjalfiella. 



Dogielia at the first sight recalls the gastrovascular system of a Cydippid, agreeing therewith 

 in all main points, as the describer. Prof. Pedaschenko, has not failed to remark. (Comp. Fig. 7, 

 reproducing Fig. i. Tab. I, of Pedaschenko's memoir). The vertical plates at the ends of the vessels 



("Korperaste") contain the genital organs, arranged in the 

 usual way, the male genital organs along one side, the female 

 organs along the other side; doubtless they represent the costse 

 of typical Ctenophores, as maintained by Pedaschenko. 

 They do not, however, carr\- swimming plates; accordingly it 

 is suggested that the animal moves only through the con- 

 traction of the muscular elements found in the jelly. These 

 muscular elements are rather well developed, the author dis- 

 tinguishing both longitudinal and circular muscles. But the jelly 

 itself is remarkably little developed, and still more remarkable 

 „ . , , ,„, ,. „ , is the ectoderm of the animal. "An der Gallertoberflache ist 



Fig. 7. Dogielia ma/nyaiia, ca. * li. rrom Peda- 

 schenko, who, however, places the animal weit uicht iiberall eiu gesondertes Epithel zu sehen, sei es als 



in the inverted position. .. ,r--i.«-i 1 ^ ■ 1 1 



erne ihr aunigende sehr feme Membran oder als emzelne sehr 



abgeplattete Zellen. An einigen Stellen findet man zwar an der Peripherie Zellen, jedoch hangen sie 

 mit der Gallerte zusammen. Sie liegen in der Gallerte, wenn anch in ihrer oberfliichlichsten Schicht 

 und sind von ihr durch keine Demarkationslinie getrennt . . . Bald findet man sie auf Schnitten ein- 

 zeln, bald mehrere auf einer geringen Strecke. Es sind aber audi grosse Strecken der Gallertober- 

 flache durchaus kernfrei. Diese Thatsachen fiihren niich zur Vermuthung dass die Gallerte eiu Pro- 

 dukt des ausseren Epithels hauptsachlich ist, welches dabei im oralen Korperabschnitte zum grossten 

 Theil aufgebraucht wird". (p. 22 — 23). — This condition of the ectoderm is, indeed, exceedingly remark- 

 able. The two photographic figures of sections (Tab. II, Fig. 4 and Tab. Ill, Fig. 6) accompanying 

 Pedaschenko's memoir decidedly give the impression that the animal has no ectoderm at all; only 

 some slight remains of jelly are found in the more protected spots. Instead of this paradox — an 

 animal without ectoderm — the true explanation of Dogielia malayana seems to me to be that it is 

 really the gastrovascular system alone of a Cydippid, the whole jelly and ectoderm (and 



