HYDROIDA 



29 



"Ingolf" St. 40. 62°oo' N., 2i°36' W., depth 845 fathoms, 4. f^, C 



- - 86. 65°o3'6 - 23°47'6 - - 76 - ? 



- - 87. 65°o3'2 - 23°56'2 - — no — ? 



- 106. 65°34' - 8°54' - _ 447 _ ^ o°6 C. 



- - 127. 66°33' - 20^05' - _ 44 _ 4, 5% . 



- - 143- 62°58' - 7°o9' - - 388 - -- 0=4 - 

 Of a type Hke that of Tiihularia curniicopia Bonne vie from the localities: 



"Ingolf St. II. 64^34' N., 3i°i2' W., depth 1300 fathom.s, + i°6 C. 



- - 18. 6i°44' - 3o°29' - - 1 135 — + 3°o - 



Gen. Corymorpha M. Sars. 



Solitary hydroids, whose contractile hjdrocaulus is surrounded by a flexible, thin, and membran- 

 aceous perisarc. The hydrocaulus is attached to the substratum by numerous rhizoids. The structure 

 of the polyp is radially symmetrical with two main whorls of tentacles, a proximal or basal whorl 

 of long tentacles supported by a mesogloeal ring in the pol)p body, and a distal whorl of short ten- 

 tacles round the orifice. In the full-grown polyp all the tentacles are filiform; in the actiuula 

 larva at any rate the distal (oral) tentacles may be capitote. The gonophores are generally supported 

 by blastostyles ; the gonangia arise from the body of the polyp between the tentacle whorls. 



As early as 1909 I stated this limitation of the genus, grouping at the same time the species, 

 on the ground of gonophoral matters, in four subgenera. However, I suggested that, as to the rela- 

 tions between the two subgenera Moiwcaultts and Lai/ipra^ a closer inquiry was wanting. As a matter 

 of fact, one of the species stated by A lima n (1876) Monocaulus grociilaudica really proves to be 

 identical with two of the species of Laiiipra stated by Bonne vie (1899). Also the other northern spe- 

 cies of Moiiocaiiliis has met a peculiar fate, being first ranked by A 11 man (1872) within his genus as 

 Mo7iocaulits glacialis (M. Sars), and afterwards (1876), after the examination of some specimens from 

 the museum of Copenhagen, described as a new species, Avialthaca islandica All man. 



These matters, indeed, throw a glaring light on the unmaintainability of the subdivision into 

 so-called "genera" to which Corymorpha has been the subject. At the first glance it is a matter of sur- 

 prise that Stechow (1913) still tries to maintain the old genera. Indeed, in zoology more considera- 

 tion must be given to the observations made on living individuals than has hitherto been done. Thus 

 the two main criteria turned to account by Stechow (1912) for the purpose of distinguishing Cory- 

 morpha 6'«;'j-/y Steenstrup (1854) and Corymorpha vardocnsis Loman (1889) testify to the fact that 

 matters of contraction are still allowed to plaj- a prominent part as to the limitation of species. By 

 the observation of a living Corymorpha it will soon be ascertained that, by extension and contraction 

 of the lower parts of the polvp and of the upper sections of the stem, the same polyp will show now 

 a more emphatic distinction from its stem, uow a smoother transition into it. The points of difference de- 

 lineated by Stechow (1912, Taf. 12, Fig. 2 and 3) are, in this respect, not so great as those which 

 may be observed in a single individual while alive. The other main character, that the spadix of the 



