PENNATUUDA. 



I have followed Kolliker in regard to the terminology; some of his terms have been used 

 from much older times, and are based on the external [resemblance to a feather, especially conspicuous 

 in forms like Pennatula, Pteroeides etc. The stem of the colony is accordingly divided into the 

 shaft, rhachis, carrying all the individuals, and the peduncle, which is naked and under natural 

 conditions sunk into the bottom of the sea; polyp is the name used only for the individuals posses- 

 sing the entire equipment of an octocoral, tentacles etc., zooid for the dwarf individuals wanting 

 sexual organs and tentacles (only in Umbellula do they carry one tentacle). The individual is said to 

 be provided with a calyx, when the basal part of its body 1 ) is stiff so as not to be retractile, but 

 the upper part of the polyp with mouth and tentacles can be retracted and hidden in it. The upper 



edge of the calyx may be more or less marked, in the former case it is 

 provided with lobes, up to eight in number; the axial (dorsal) side of the 

 individuals is turned towards the stem, the ab axial (ventral) away from 

 the stem. Wings, alse or pinnae, is the name of the oblique series of 

 polyps placed transversely on the stem, where the polyps are mutually 

 coalesced. 



I have differed only in one point from Kolliker ; what he d e - 

 scribes as the ventral side of the colony, I call the dorsal, and 

 vice-versa (except in Rcnillce see below); this I shall try to explain more 

 closely. 



In the great majority of Pennatulids the colony, as is well known, 

 is constructed bilaterally. The plane that divides the stem longitudinally 

 into two corresponding parts, has quite naturally always been interpreted 

 as a dorso-ventral one (VD in the annexed figure); but whether the 

 side of the stem in the figure denoted by Z>, is to be called the dorsal (po- 

 sterior), or the ventral (anterior), has always been decided quite arbitrarily. 

 The earlier authors -- with the exception of Lamarck -- have generally 

 called it the dorsal, or posterior side. Kolliker, in his monograph (p. 5), 

 declares it to be the ventral for no other reason than that it is am 

 zweckmassigstens. Later, all authors have adopted the decision of Kolliker 



although some of them (e. g. Verrill, Koren and Danielssen) had earlier used the contrary desig- 

 nation. The feature distinguishing this side of the colony, is first and foremost that new polyps 

 develop on either side, away from the median line; thus, the polyps placed nearest to this line are 

 the oldest in each transverse series; further, the median line itself is always sterile in so far as 

 polyps are never formed in it; only rarely is it covered with zooids (for instance Kophobelemnon\\ 

 generally along the median line there is a more or less narrow naked streak, increasing in breadth 

 down towards the peduncle. 



The opposite surface of the stem ( V in the figure) is characterized by the fact that the new 

 polyps are developed from both sides in the direction towards the median line; accordingly, the 



Fig. i. 



Diagram, part of a Penna- 

 tulid-rhachis. VD indicates 

 the direction of the middle 

 plane, i 8 polyps in one 

 transverse series; the figures 

 give the age of these polyps, 

 no. i being the eldest one; 

 the arrows indicate that the 

 polyps accordingly appear 

 and are developed to either 

 side away from the naked 

 streak D ~D. 



") By the body of the polyp is understood the part of the polyp projecting from the surface of the stem; in reality 

 some portion of each individual issuing from the stem is inclosed in the latter. 



