7. Anthozoa (incl. Hydrocorallia). A. Zoantharia. 25 



differentiated; the middle c.-g. trafct above mentioned may be called the spirocyst- 

 glandular tract, from the presence of numerous thin-walled nematocysts (spiro- 

 cysts) and mucus-cells. The wavy filament on the sterile mesenteries of the 3d 

 and 4th cycle, and its analogue on the fertile mesenteries, may retain the name 

 cnido-glandular tract, having numerous, large and broad, thick-walled uemato- 

 cysts, and of closely packed, granular gland-cells. The spir.-gland. tract is a 

 direct continuation of the ridges of the stomodseum ; the ciliated tracts one on 

 each side, are continuations of the ectoderm and mesogloea in the furrows of 

 the stomodaeum. The median tract is either an undivided structure (as in 

 Botrucn. norvegicus), or is separated by a ciliated groove into two well-marked 

 streaks in which the gland-cells and spirocysts are aggregated (as in Ce. membr., 

 lloydii, P. solitarius, multiplicatus, mana, and Ceriantheopsis amer.) or presents 

 intermediate conditions. In the aboral part this differentiation disappears in 

 the series C. membr. - G. amer., so that the median streak is like that of 

 B. norv.', but in Arachnactis lobiancoi [see below, Carlgren (3)] and albida, 

 and in Arachnanthus , the ciliated groove is always present between the two 

 portions of the median streak. The author applies the name craspedion to 

 that part of the filament where the spir.-gland. tract is simple and without 

 ciliated tract. The form and structure of this region vary in different genera. 

 Craspedonemes may be developed from the ciliated tract region of the 

 mesenterial filaments, as also from the cnido-glandular tract and from the 

 craspedion region; they are flat or rounded in transverse section, and in the 

 middle possess endoderm and a mesogkeal axis, and are covered on the greater 

 part of the free edge, by a part of a filament which usually exhibits an as- 

 cending and a descending limb. The craspedonemes of the ciliated tract region 

 are of two knids - - (1) normal, which occur in many species, usually in large 

 numbers, and in some species are aggregated, at the aboral end of the ciliated 

 tract region, forming bunches; (2) those which possess only an ascending limb 

 of the filament, e. g., in the most aboral craspedoneme of Paohyc. mana, in 

 which the filament in the course of its growth, has evidently not yet reached 

 the aboral side of the craspedoneme. Craspedonemes arise more rarely from 

 the cnido-glandular tract, and only on mesenteries on which the c.-g. region 

 is extremely slight, e. g. , in certain mesenteries of P. solitarius and C. lloydii] 

 the wavy coils of this tract correspond to the bunches above described on the 

 ciliated tract region, though the former are not so thread-like. The craspedo- 

 nemes of the craspedion region are either (1) acontia* (e. g. in Arachnanthus], 

 or (2) undifferentiated , with mucus-cells and spirocysts, but which have also 

 developed granular gland-cells and thick-walled nematocysts. These are known 

 only in C. amer. The acontia (van Beneden) have the same structure as 

 the craspedonemes of the ciliated tract region of G. membr., i. e., they are 

 composed of an ascending and a descending limb of the filament, which encloses 

 an endodermic process of the mesentery, but this endoderm, in the distal portion 

 of the acontium, almost or entirely disappears. The chief portion of these 

 acontia is ectodermal, being derived from the craspedion, and contains gland- 

 and mucus-cells, but nematocysts are rare. These acontia are therefore not 

 sting-batteries, like the acontia of Actiniaria. Botrucnidae (van Beneden) are 

 aggregations at the aboral end of the mesenteries and on their free edge in 

 Botrucn. norveg. and in certain larval forms. Each grape-like body cnido- 

 rage is not simply epithelial (van Beneden), but contains basally meso- 

 gloea, often in the form of a cup or funnel. These organs, which contain thick- 

 and thin- walled nematocysts, are ectodermal and homologous with the > acontia 

 and craspedonemes described above. 



