. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. 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 gonothecse and the outer protective network of the tubes. Grammaria abietina thus presents an intermediate stage between types with uniform, hermaphr
. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. 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 gonothecse and the outer protective network of the tubes. Grammaria abietina thus presents an intermediate stage between types with uniform, hermaphroditic coppinia;, 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- gether female aggregate. The gonophores in Grammaria abietina 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 richly developed colonies which, owing to the somewhat divergent character of the hydrotheca, are here noted as representatives of a particular form, forma bremcyatha 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 tvpiea, 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 brevicyatha,cm 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 specif
Size: 1361px × 1837px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectscientificexpedition
