7 o 



CTENOPHORA. 



observations is doubtless this, that his supposed specimens of PI. rhodopis are not this form at all, but 

 most probably belong to some species of L,obatse. This suggestion is supported by the fact, that in 

 Garbe's material of young Plenrobrachise from Helgoland were found a pair of specimens showing 

 essentially the same structure of the gastrovascular system as his "PI. rhodopis" from Triest. Now it 

 can be said with rather great certainty, that these latter young Ctenophores from Helgoland can only 

 be young Bolinainfundibtilum, the only other tentaculate Ctenophore occurring here besides Pl.pileus. 

 It is in good accordance herewith, that the costse are placed very close together, as is characteristic 

 of the young Bolina (which was even named Cydippe quadricostata by Sars on account of this pecu- 

 liarity). I think then that there can be no doubt that Garbe's Pleurobrachia rhodopis is really 

 the young of some species of Lobatse (evidently not Bolina, since the specimens from Triest differ in 

 some points from those from Helgoland). The mistake is not to be wondered at very much, it 

 being in fact a very difficult matter to distinguish such very young specimens of Lobatse from true 

 Cydippids. Garbe's observations thus cannot disprove the identity of PL rhodopis with Pl.pileus, 

 which I think has been conclusively established. 



inf.c. 



ph. - -/ 



P'ig. 13. a. b. Pleurobrachia pifetts, showing different relations of the gastrovascular system and tentacle bases, due to 

 different stages of contraction, ar. v. adradial vessel; d. diaphragm; inf. infundibulum ; inf. c. infundibular canal; ir. v. inter- 

 radial vessel; m. mouth; m. v. meridional vessel; oe. oesophagus; ph. pharynx; ph. f. pharyngeal (stomodaeal) folds; ph. v. 

 pharyngeal vessel; t. b. tentacle base; tr. v. transverse (perradial) vessel; t. sh. tentacle sheath; t. v. tentacle vessel. 



In the work quoted, on the Ctenophores of the German South- Polar Expedition, Dr. Moser 

 points out the great variability found in this species in regard to the shape, size and position of the 

 different parts of the body. All transitional forms occurring together at the same locality, these differ- 

 ences must be referred to "individuelle Schwankungen und Kontraktionszustaude, . . . Altersunterschiede 



und . . . die verschiedenen Konservierungsmethoden" "Die Untersuchung deutet darauf hin, dass 



mit dem Alter die Form vielfach mehr zylindrisch wird, der Magen sich im Verhaltniss zum Trichter 

 sehr verlangert und die Tentakelbasen grosser werden und sich ersteren uahern. Beriicksichtigt rmiss 



