1895- RESULTS OF ^'CHALLENGER'' EXPEDITION. 41 



vol. xxvi. As the beautiful Naples monograph of Andres appeared 

 before the supplement was written, R. Hertwig had the opportunity 

 to discuss the scheme of classification and the systematic criteria 

 adopted by that naturalist, and to suggest a scheme of classification 

 of the whole group that later research has done little to modify. 



Undoubtedly the most interesting individual anemones obtained 

 by the " Challenger," were the forms called Corallimorphidae by 

 Moseley. In these, several features, usually present in anemones, 

 are replaced by features more characteristic of corals. The tentacles 

 are arranged in radial rows, so that several of them open into the 

 same radial cavity ; the disk is stiff and leathery, and has no sphincter 

 muscle by which it may be drawn up like a bag closed by a string 

 over the retracted tentacles ; the nematocysts are peculiarly large. 

 From examination of these and of some other pecuUar forms, Hertwig 

 reached the conclusion that the old distinction between the corals or 

 sclerodermatous anemones, and the soft-skinned, or true anemones, 

 is not morphological, and he inferred that as knowledge of the soft 

 parts of the Sclerodermata is obtained they will gradually be distri- 

 buted among the different groups of anemones. 



The anemones he divided into six main groups, well-marked off 

 by important structural features. These are the Edwardsias, Ceri- 

 antheae, Zoantheae, Paractiniae, Monauleas, and Hexactiniae. The 

 last group contains by far the largest number of forms. 



In the hexactinians there is a great dichotomy between those 

 like the Corallimorphidae, with double or multiple wreaths of tentacles, 

 and those in which the tentacles form a single wreath. The former 

 group is the less known, and to it probably belong a number of the 

 stinging anemones of tropical seas, the anatomy of which is imper- 

 fectly known. Hertwig showed that the old distinction between 

 anemones with retractile, and anemones with non-retractile tentacles, 

 should be replaced by distinctions based on the presence or absence 

 and the character of the sphincter muscle. 



The material at Hertwig's disposal was neither large enough nor 

 sufficiently well-preserved to complete the working out of the group, 

 but there is no question but that he has laid the foundation for future 

 investigation. With his reports and the monograph of Andres, which 

 however, deals chiefly with external characters, those who have an 

 opportunity of studying actinians will find the way prepared for most 

 interesting and valuable investigations. 



P. Chalmers Mitchell. 



In the group of the Hydroidea no very important results were 

 obtained. A few interesting new genera were found, and some 

 remarkable points in geographical distribution referred to ; but the 

 collection was not a large one, and the results obtained from its 

 examination present no features of special interest. The Hydro- 

 medusae and Scyphomedusae, however, were the occasion of very 



