20 



HYDROIDA II 



in the defensive polyps and elsewhere, large, practically cylindrical nematocysts in addition to the small 

 capsule form which is found in all thecaphores; the nematocysts are thus dimorphous. A remarkable 

 feature about the coppinia is the position of the male gonothecse, which here appear as stalked, oval 

 to spherical formations between the closely packed female gonotheca; and the outer protective network 

 of the tubes. Grammaria ahictina thus presents an intermediate stage between types with uniform, 

 hermaphroditic coppiuise, where the male gonothecse are wedged in among the female, and those 

 where the male gonothecse appear singly outside the coppinia or scapus, which has become an alto- 

 o-ether female aggregate. The gonophores in Grammaria abictina exhibit distinct sexual dimorphism; 

 the female gonophores are heteromedusoids, the male cryptomedusoids. The cryptomedusoid gono- 

 phore is, however, here highly reduced, and distinctly presents a transition stage which would, on 



slight further reduction, become a styloid gonophore. 



From two places at the Faroe Islands we have in the material some very 

 richlv developed colonies which, owing to the somewhat divergent character 

 of the hydrotheca, are here noted as representatives of a particular form, 

 forma brcvicyatha nov. In point of habitus, the mentioned colonies differ 

 but little from forma typica, they are of equally robust build, and with the 

 same rich ramification; on closer examination, however, one cannot fail to 

 observe the remarkable short hydrothecse (fig. V). In forma typica, the 

 hydrotheca protrudes its distal parts out in front of the stolons so far that 

 the free portion of its upper (adcauline) wall reaches a length of 1,5 to 3 

 times the diameter of the aperture; in forma brrvicyat/ia, on the other hand, 

 the corresponding part is only one-half to one diameter in length. This 

 might perhaps by some be regarded as a good specific character. We find 

 however, here and there among the colonies, hydrothecse presenting the same 

 features as forma typica ^ and, in slightly greater numbers, intermediate 

 forms with lengths filling the interval between the dimensions named. On 



Fig. V. Grammaria abh-tina 



forma brevkyatita. Terminal the Other hand, these intermediate forms, and ^Hypica''^ hydrothecce occur 

 part of of a branch. Colony ^. j^^ ^^^ ^^ .^ ^ percentage among the colonies that they exert no influ- 



froni7mile.s N.byE.ofMygge- .? fe i' & t. J 



nK.s point, the Faroe Islands, ence upon the general character of the colony as a whole. How far we have 



57 fathoms. (X 40.) , i 1 • , 1 , • , i • 1 -^i ^ ■ l. 



liere to deal with a local variant group, cannot be determined with certainty; 

 that the form can hardly be very common in the northern seas is evident from its rare occurrence 

 ill the extensive material now being dealt with, even when this is supplemented by the large collect- 

 ions from Trondhjem Fjord. Still, the form in question cannot be summarily disposed of by noting 

 it under the head of casual single variants, since it occurs in a single colony from one place, but in 

 four remarkably luxuriant ones from the other. 



Forma brcvicyatha exhibits certain resemblances to Grammaria immcrsa Nutting; there are, 

 however, so considerable differences observable that the two cannot be confused. The latter species is 

 immediately recognisable from its finer structure, whereas Grauniiaria abictina is a species of very 

 coarse build. The splitting of the tops of the branches (fig. V) in forma brevicyatha also agrees 

 with Gramtnaria abietina^ as distinct from Grammaria immersa. A certain likeness to the latter species 



