ATLANT. DEEP-SEA EXPED. 1910 VOL. Ill) 



CTENOPHORA 



inner wall of the body (textfig. 2); also longitudinal mus- 

 cles are distinct, especially in the aboral part. All these 

 crossing fibres form together a close, somewhat regular 

 meshwork. The muscle cells show some very peculiar 

 protoplasmic swellings (PI. I, fig. 12), looking almost like 

 a ganglionic chain of an Arthropod. Several of these 

 swellings may be found on the same thread, in irregular 

 distances. Branching of the muscle cells has not been 

 observed, but very probably will be found at their ends. 

 They are all rather much folded, nearly spirally; this is 

 evidently the result of contraction on preservation. Amoe- 

 boid cells are very scarce in the jelly. 



Granular cells are exceedingly numerous in the sa- 

 gittal folds of the pharynx, while the true pharyngeal 

 folds contain such cells only in very small numbers. 



The colour is now yellowish, semitransparent; ori- 

 ginally it was more red, the colour being bound to the 

 folds of the pharynx. 



The nearest relative of this very interesting Ctenophore 

 is evidently, the "Mertensia" Chuni, for which I have 

 established ("Ingolf" Ctenophora, p. 36) the genus Ba- 

 thyctena. Like Aulacoctena it has proliferations from the 

 meridional and pharyngeal vessels, a feature otherwise not 

 known among tentaculate Ctenophores. The pharyngeal 

 walls are strongly folded in Bathyctena; but i does not 

 appear from Dr. Moser's description, whether these folds 

 are arranged in the same way as in Aulacoctena. Through 

 the kindness of Professor Vanhoffen I have had oppor- 

 tunity to see the two specimens of Bathyctena from the 

 German South Polar Expedition. The condition of these 

 specimens does not permit any further preparation, but 

 I observed in the [pharynx of the larger specimen a pair 

 of whitish lobes ending, where the widening of the pha- 

 rynx begins. These lobes, which are not indicated in 

 the figure (Taf. XX, 3) given by Dr. Moser, I am incli- 

 ned to regard as corresponding to the sagittal pharyngeal 

 folds of Aulacoctena. There seems also to be an indi- 

 cation, that they are separated in the middle line. In the 

 smaller specimen these lobes could not be observed. 

 Whether the development of folds in the pharynx is 

 mainly the same in both forms or not, I think that the 

 character of the proliferating meridional and pharyngeal 

 vessels is important enough to justify the establishment 

 of a separate family for these two forms. I shall give 

 here diagnoses of this family and the two genera belong- 

 ing to it. 



Bathyctenidse n. fam. 



Tentaculate Ctenophores, compressed after the sagittal 

 plane. Proliferations from the meridional and the pharyngeal 

 vessels. The pharynx walls strongly folded. Tentacle sheath 

 opening orally. Jelly very tough. Deep-sea forms. 



1. Bathyctena Mrtsn. 



Body rounded; no lateral furrow. Apical organ not 

 sunken. Pharynx in the lower part strongly widened in the 

 transversal plane. 1 ) No lateral processes from the tentacular 

 basis. 



Only species known: B. chuni (Moser). 



2. Aulacoctena Mrtsn. 



Body ovate, with a deep lateral furrow and an apical 

 prolongation, deeply invaginated; the apical organ lies in 

 the bottom of the invagination. The pharynx not widened 

 in the transversal plane in the lower part. The upper 

 part of the pharynx with strongly developed sagittal folds. 

 The subsagittal adradial vessels issue directly from the 

 infundibulum, the subtransversal issue distally, at the sides 

 of the tentacle basis. Proliferations also from the adradial 

 vessels. Tentacle basis with lateral processes. Tentacles 

 simple, with a terminal knob. 



Only species known: A. acuminata Mrtsn. 



It still remains to consider the question, to which 

 group of the other Ctenophores the Bathyctenidae are 

 related, the sagittal compression decidedly suggests the 

 Mertensiids as their nearest relations, as is also expressed 

 in the fact that Bathyctena was originally refered to the 

 genus Mertensia. The proliferations of the meridional 

 and pharyngeal vessels certainly recall the Beroids, but the 

 fact that the deep-sea forms are tentaculate at once shows 

 that this is merely an analogous development, the proli- 

 ferations having developed independently in both Beroids 

 and Bathyctenids. It is worth recalling that Mertens 2 ) 

 states to have observed in Mertensia ovum „baumartig 

 verzweigte Gefasse" proceeding from the upper part of 

 the subtransversal meridional vessels towards the inner 

 part of the gastrovascular system. If this proves to be 

 correct, it will, evidently, mean another connecting point 

 between the Mertensiids and the Bathyctenids. 



With the Pleurobrachiidae and the Cestidae the deep- 

 sea forms show no nearer relation; with the Lobatae and the 

 Platyctenidae they have the large oral lobes in common. 



Our present knowledge evidently leads to the conclu- 

 sion that the Bathyctenids are derived from the Mertensiids, 

 along the same line as the Lobatae and the Platyctenidae. 



') This diagnosis is, of course, not complete; but in the present 

 state of our knowledge it seems not warranted to extend it and give 

 any definite statement about the arrangement of the gastrovascular 

 system. 



2 ) H. Mertens: Beobachtungen und Untersuchungen iiber die 

 beroeartigen Acalephen. Mem. Acad. Imp. St. Petersbourg. Ser. 6, 

 Vol. 2. 1833. (See also; Ingolf-Ctenophora, p. 63). 



