ACTINIARIA 



79 



4 in each mesentery). Commonly they are found in the middle or in the outer rim of the mesenteries. In 

 the section reproduced in the textfigure 96 the stomata have been liit, and the mesenteries thus disconti- 

 nued. The filaments appear only on the 8 to 10 perfect mesenteries. The ciliated streaks are very long, but 

 discontinuous as in Scytophorus antarcticus and I soedwardsia mediterranea, and thus divisible into several por- 

 tions along the middle streak. The textfigure 97 shows a transverse-section through a mesentery with a 

 testes follicle and a rather well developed middle streak; a little farther down, towards the proximal 

 end, we find rather well developed ciliated streaks (textfig. 98) which are still more distinctly seen on the 

 following transverse-section (textfig. 99). In a transverse-section stiU farther down (textfig. 100) we meet 

 several testes follicles, but only a rather inconsiderable middle streak. In the following sections we again 

 find the middle streak (textfig. loi). The filaments are, as for the rest, of usual structure, and the cnido- 

 glandular tract thicker than the middle streak. Three examined specimens were males, a fourth one a female. 

 The reproductive organs were well developed, especially in the specimens with 10 perfect mesenteries. 



Biology: The animal lives on clay bottom, and on account of its particular structure it might very 

 weU ha\-e the habits of a worm. Probably it pushes deep down into the clay, for it is worth noticing 

 that I have observed the animal only one summer when we used a deep-going dredge, constructed by 

 Professor Tulll^erg, at the zoological station of Kristineberg, and never during the many others summers 

 I spent at the station. With its proximal end it is able to penetrate into the clay as the Edwardsids and Hal- 

 campids; but also the distal end possibly .ser\^es as a boring organ. As the tentacles are wanting, the animal 

 must take its food in another way than the other Actiniaria, it is therefore possible that it feeds upon detri- 

 tus-particles in the clay, though I have not found any such in its coelenteric cavity. It is besides reasonable 

 to suppose that the .strongly tliickened oral disc with its numerous spirocysts ("Klebkapseln") has under- 

 taken the function of the tentacles as capturing apparatus. 



The occurrence of a really tentacle-lacking Actiniaria is thus established. True enough, R. Hert- 

 wig (1882, 1888) has believed himself to have discovered forms, among the Actiniaria from the Challenger 

 Expedition, which were tentacle-lacking or with ver>' reduced tentacles, but these observations have appear- 

 ed not to be correct. The tentacle-lacking Actiniaria, described by R. Hertwig, are namely to be referred 

 to forms having thrown off their tentacles (Mc. Murrich 1893, Carlgren 1899), and those with strongly 

 reduced tentacles, provided with large stomidia, to forms, the state of preservation of wliich leaves a great 

 deal to be desired. (Compare Sicyonh crassa). In the cases where the bad preservation of the animals has 

 made it impossible to perform a control-examination we may resort to a similar kind of explanation. In 

 some cases recorded by Hertwig — as far as I remember especially of Polyopis — it is possible that the 

 tentacles were invaginated before they were macerated. In the genus Halcampoides it namely often happens 

 that some tentacles, rarely all, become invaginated on preservation. In the latter case, when aU tentacles 

 are invaginated, it looks as if they are wanting, and only large stomidia remaining. Ver>- smaU tentacles 

 we find in some Discosomids, especially in Discosoma Unguja. Here the tentacles, arranged in radial rows, 

 do not reach the surface of the oral disc, but are indicated by invaginations in the mesogloea of the oral disc. 



Systematic remarks. I have placed this family among the Athenaria because of the structure 

 of its proximal end and of that of its mesenteries. The presence of ectodermal muscles and of spirocysts in 



