CTENOPHORA. 67 



I would remark to this whole reasoning, that it is scarcely justifiable to lay so much stress 

 on the description of the young stages of M. ovum given by Agassiz. As pointed out above, there 

 is no statement about the size of the specimens figured, so that a direct comparison with the figures 

 of IMertens' Beroe octoptera cannot be duly carried out — and upon the whole, it can scarcely be 

 taken as a sure fact that all the figures given by Agassiz are really the same species. I would not 

 find it justifiable either to lay so much stress on the presence or absence of some pigment spots, at least 

 in these old and imperfect descriptions and figures. Further, as I think it has been proved beyond 

 doubt that B. covipressa is really identical with M. ovum, the same must, of course, be the case with 

 B. octoptera, which is almost certainly the young of it. 



While I am thus decidedly of opinion that the Bcroe comprcssa and octoptera of Me r tens 

 are only synonyms of Mcrtensia ovum, against the view held by Moser, I willingly agree that 

 especially the large aboral processes indicate a relation to the genus Callianira, as was formerh- 

 thought by Chun (Monograph, p. 279; in the "Ctenophoren der Plankton-Expedition" this view is 

 dropped), and recently maintained by Moser. In fact, I think it very probable that the two genera 

 Mertensia and Callianira will prove to be nearly related, belonging to one and the same family, the 

 Mertensiidse. The character upon which Chun established the two families, MertensiidcB and Calliani- 

 ridcp, is the presence or absence of the apical processes, it being evidently due to the unsatisfactory 

 description and figures of Agassiz that they are taken to be absent in Mertensia ovum. Since, how- 

 ever, they are really present in Mertensia as well as in Callianira it can scarcely be doubted that 

 these two genera must really belong to the same family, which must, of course, keep the name 

 Mertensiidcc, the diagnosis having to be altered accordingly into "apical processes present". Whether 

 there are other features of the rank of family characters must be left undecided, until the much 

 needed closer study of the anatomy of Mertensia ovum has been undertaken. 



To the family Mertensiidae Chun (Monograph) also referred the genera Euchlora and Cha- 

 ristephane and later on (Ctenophoren d. Plankton-Expedition) the genus Tinerfc Chun. That this 

 latter form really belongs to this family seems evident enough. As for Charistephane., which is very 

 probably only a larval form (with dissogouy) of a Lobate or Cestid, as suggested by Chun (Monograph, 

 p. 278), it must be left undecided to which family it really belongs. For Euchlora, characterized especiall\- 

 "by the opening of the tentacle sheath at the oral pole of the body and, perhaps, by the unbranched 

 tentacles (it is not quite certain that they are so in Euchlora filigera Chun), it seems necessary to 

 establish a separate family, Euchloridae n. fam. To give the full diagnosis of this family is also im- 

 possible at the present stage of our knowledge; a closer study of Etichl. filigera and especially of the 

 structure of the tentacles of both species is needed. That there are no cnidoblasts, as is stated by 

 Chun, may be taken as certain, but it is as )et unknown whether the tentacles are provided with 

 colloblasts of the usual ctenophoran structure. To the family Euchloridse the genus Dryodora Ag. 

 would also seem to belong. (It is referred by Moser to the Mertensiidae, together with Euchlora). 

 Especially its simple tentacles and the lacking of the pharyngeal folds indicate a closer relation to 

 Euchlora. It is, however, too little known, our knowledge resting alone on the description and figures 

 given by Mertens, so that its true position must remain somewhat uncertain as yet. 



