. STYLASTERIDAE (HYDROCORALS) FROM SOUTHERN SEAS 37 between the spines. In the terminal branches all intermediate stages occur (see Broch, 1942, p. 44), and von Marenzeller (1903) was accordingly inclined to consider the small pores only as developmental stages of the larger pores of the spines. It is impossible from examination of dried specimens alone to solve this question or to determine whether a real dimorphism exists. But investigation of the soft parts shows that the dactylozooids also exhibit a dimorphic development correlated with the type of pore. The dactylozooids inhabiting the si
. STYLASTERIDAE (HYDROCORALS) FROM SOUTHERN SEAS 37 between the spines. In the terminal branches all intermediate stages occur (see Broch, 1942, p. 44), and von Marenzeller (1903) was accordingly inclined to consider the small pores only as developmental stages of the larger pores of the spines. It is impossible from examination of dried specimens alone to solve this question or to determine whether a real dimorphism exists. But investigation of the soft parts shows that the dactylozooids also exhibit a dimorphic development correlated with the type of pore. The dactylozooids inhabiting the simple pores of the coenosteum are digitiform (Fig. 1) and lack a specially developed basal adhesive part attached to the bottom or wall of the pore. The dactylo- zooids of the ' large pores', or grooves of the spines on the other hand, have a long basal segment attached to the wall of the lower part of the groove and the outer part of the adjoining pore, the digitiform, free part of the dactylo- zooid arising from the middle of the basal segment (Fig. 2). In the Discovery specimens the contracted free part is shorter than the basal segment, and it is impossible to judge of its length when extended. We must, however, presume that its powers of extension are rather large. Thus it appears that a real dimorphism exists among the dactylozooids of E. antarctica correlated with the dimorphic 2 development of the dactylopores. _,. _ „ , r . - rigs. 1, 2. Ernna antarctica from bt. 652. The male ampullae contain a tew gonophores (generally three) (^ simple, digitiform dactylozooid from in different stages of development. When one gonophore is quite Pore between the spines. (2) Dactylozooid 0 11 1 • j\ from the groove of a-spme; the digitiform, ripe and about to discharge its contents, the smallest (third) free part of the zooid (z) arises from the gonophore is only a rudimentary bud. No blastostyle can be middle of a large, adhesive basal part (/;). detected in the ampulla. In this re
Size: 1792px × 2789px
Photo credit: © The Bookworm Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, booksubjectocean, booksubjectscientificexpediti
