232 BULLETIN OF THE BUREAU OF FISHERIES. 



have contributed materially to this end may be mentioned the following: Hertwig, 

 R. and O. (1879); Hertwig, R. (1882); Andre, A. (1884); McMurrich, J. P. (1894); 

 Van Beneden (1897); Carlgren (1900). These works are devoted almost exclusively 

 to the Actinozoa. Similar work upon the Alcyonaria has been done by May (1899), 

 Kukenthal (1905), and Studer. 



While it is no part of the purpose of this report to enter into the matter of taxonomy 

 in any detail, it may not be amiss to include brief synoptic tables indicative of opinion 

 as to this phase of our subject, at least, as relates to Actiniaria. A valuable review of 

 the history of taxonomic development along this line may be found in the report of 

 McMurrich on the Actiniae of the Albatross Expedition (Proceedings, U. S. National 

 Museum, vol. xvi, 1893, p. 1 19-135). Brief historical references are also made by 

 Hertwig (Challenger Report, vol. vi, p. 16-18) to this phase of the general subject, though 

 with no attempt to trace the development of taxonomic systems. 



Concerning the systems proposed by Van Beneden (1897) ^°d Carlgren (1900), it 

 is hardly within the scope of this paper to undertake an adequate review. Both are 

 noteworthy contributions and will command the attention of specialists everywhere. 

 They involve, however, considerable of embryological and histological details and 

 methods, and are hence somewhat too technical for use in the present instance. 



Under almost all modem systems of classification the musculature of the body 

 has constituted one of the most important taxonomic characters. It becomes necessary, 

 therefore, to devote some further attention to this feature. As to their relations, the 

 muscles may be said to be ectodermal, entodermal, or mesodermal, as they are associated 

 with these several tissues. The musculature is disposed chiefly in two positions, namely, 

 (i) as longitudinal fibers distributed to the walls of the column; (2) as circular bands 

 distributed variously over the body. Of the latter there is usually a special development 

 in the oral region known as the sphincter. This acts as an organ for closing the mouth, 

 much as one might close the opening of a bag by a draw string. 



R. Hertwig has emphasized the importance of various aspects of the musculature as 

 taxonomic features and says: 



The nature of the sphincter varies greatly. We talk of a diffuse sphincter when it arises from 

 repeated pleatings of the muscular lamella; in that case because it is not sharply defined at the upper 

 and lower margins, it does not strike the eye in looking at the surface, and is shown in transverse 

 sections only by the local thickening of the wall in whose substance it is completely embedded. A 

 circumscribed sphincter is formed ^vhen the pleated muscular mass projects above the inner surface 

 of the wall, with which it is connected only by a narrow band, so that an annular swelling arises which 

 is easily observed both in looking at the surface and in transverse section. 



Finally, in the mesodermal sphincter, the muscles have left their original position in the epithelium 

 and are completely hidden in the supporting substance, which consequently increases doubly or trebly 

 in thickness. The complete absence of the sphincter is comparatively rare. I have only observed 

 it in a few species, almost invariably animals which are not capable of contracting the upper margin of 

 the wall over the oral disk. This is, however, also the case in animals with a weak sphincter, such as 

 the Antheadse. On the other hand, the existence of a strong circular muscle can often be inferred with 

 tolerable certainly from a high degree of contraction. The capacity for concealing the oral disk plays 

 an important part in the systematic division of the Actiniaria; this is generally most inappropriately 

 expressed by the term "retractile tentacles." It would be decidedly more rational to make the ana- 



