. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. 26 HVDROIDA II best exposition of the family is that given by Kramp, who has in two works (1911 and 1913) given a close description, which as regards its main features, is adhered to in the present work. Kramp (1913 p. 14) inclines to the view that the family should be divided into two, a primitive family, Cus- pidcllidiC, where the closing apparatus is formed by the upper part of the hydrotheca wall, and a more highly developed family, Campanulinida, where the closing apparatus consists of the original roof of the hydrothec
. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. 26 HVDROIDA II best exposition of the family is that given by Kramp, who has in two works (1911 and 1913) given a close description, which as regards its main features, is adhered to in the present work. Kramp (1913 p. 14) inclines to the view that the family should be divided into two, a primitive family, Cus- pidcllidiC, where the closing apparatus is formed by the upper part of the hydrotheca wall, and a more highly developed family, Campanulinida, where the closing apparatus consists of the original roof of the hydrotheca. Kramp's point of view is doubtless highly correct, but as my material is not suited to serve as basis for more detailed exposition, I have merely noted the two mentioned groups as sub- families, otherwise following mainly the generic division established by Kramp (1911 p. 383). The gouothecae in several members of the family are of considerable interest, differing only in their greater dimensions from the hydrothecse — doubtless a primitive feature. This peculiarity is known among the genera of Stcgopoma, Cuspidella, and Lafo'iina. Unfortunately, very little is known as to the gouophores, but we know that the family comprises the polyp-generation of a number of highly heterogeneous Leptomedusae, which are distributed by systematists throughout a whole series of families. As, however, the polyps, save for the mentioned characters in the sub-families, exhibit very considerable uniformity, we can hardly, from what we know at present, consent to a further sub- division of the family. We have evidently here to deal with a series of biological divergencies in the medusa generation, particularly calculated to demonstrate the impossibility of establishing, in the pre- sent state of our knowledge, any common system for the two generations. The hydroid system cannot here be adapted to the medusa system, which evidently demands thorough investigation of the biolog- ical adaptation ph
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