November 3, 1904] 



NA TURE 



19 



facts, and whoever attempts in the future to classify the 

 Zoantharia must base his conclusions upon many of the 

 anatomical details which are here for the first time 

 adequately recorded. 



No less than twenty-six species of corals, distributed 

 among twenty genera, formed the materials of Mr. 

 Duerden's investigations, and, although the descriptions are 

 not exhaustive, there is a very full and interesting account 

 of the general structure of all these forms. 



The brilliancy of the colours of many corals in the living 

 state has excited the interest and admiration of the 

 naturalists and travellers who have visited coral reefs. 

 These colours appear to be due to a variety of causes. In 

 many cases the cavities of the polyps and the adjacent 

 canals bear large numbers of the symbiotic algs called 

 Zooxanthella;. The colour of these cells accounts for most 

 of the prevailing brown and yellow-brown tints. In some 

 few instances, such as Astrangia solitaria and Phyllangia 

 americana, the Zooxanthellae are nearly or wholly absent, 

 and the polyps then are remarkably transparent and almost 

 colourless. But there are in many cases definite pigment 

 cells, both in the ectoderm and endoderm, which may add 

 to or give the only colour effect of the expanded polyps. A 

 third cause of colour is to be found in the boring filamentous 

 red and bright green algse with which many corals are 

 infested. 



The chapter dealing with the structure and arrangement 

 of the tentacles is one of exceptional interest. To investi- 

 gators in this country the tentacles have always offered 

 •difficulties and uncertainties. However carefully the 



fr'lG. I. — Diagraminatic figures showing the arrangement of the first six 

 pairs of mesenteries in (a) Madrepora ; (i5) most other species of Madre- 

 poraria. The upper side of each is the side turned towards the a.\is 

 (axial), and the lower is away from the axis (abaxialj. The axial side 

 of Madrepora is vential, whereas in most other species it is dorsal. (The 

 upper of the bilateral pairs marked v, v in a should have been VI, vi). 



material they can obtain is preserved, it is impossible to 

 prevent a great deal of retraction and shrinkage. Mr. 

 Duerden's careful observations, therefore, of the fully ex- 

 panded tentacles of his living corals form a particularly 

 welcome addition to our knowledge. 



The most elaborate, and perhaps we may say the most 

 important, part of the author's work deals with the number 

 and arrangement of the mesenteries. This is not the place 

 to relate or to criticise details which are necessarily highly 

 technical and somewhat intricate ; but it may be said that 

 it is upon the results of this part of his investigations that 

 the suggestions he has to offer for the classification of the 

 order very largely depend. 



If we regard the Madreporaria as an order, we may 

 divide it into two suborders ; — (i) the Entocnemaria, (2) the 

 Cyclocnemaria. In the former the mesenteries always arise 

 in bilateral pairs, and beyond the protocnemic stage the 

 increase takes place within one or both of the directive 

 entocoBles. In the latter the mesenteries, beyond the proto- 

 cnemic stage, arise in isocnemic unilateral pairs within the 

 primary e.xocoeles. The Entocnemaria are represented only 

 by the single section Perforata, the Cyclocnemaria by the 

 two sections Aporosa and Fungacea. The arrangement of 

 the families of the Aporosa into two groups, the Gemmantes 

 and the Fissiparantes, based upon the method of asexual re- 

 production — by gemmation or by stomoda;al fission — sup- 

 ported as it is by Mr. Duerden's later researches, can be 

 regarded as only tentative and suggestive at present; but 

 the facts upon which it is based are among the most interest- 

 ing and, important of his many results. 



NO. 1827, VOL. 71] 



It is a matter for regret, which many will share with 

 the reviewer, that in the introduction to the systematic part 

 of the memoir Mr. Duerden has not given us his views as 

 to the relation of the Actiniaria to the Madreporaria, a 

 difficult matter upon which no one is more competent to 

 express an opinion. 



There are some points in the terminology employed by 

 Mr. Duerden that appear to me to be open to some objec- 

 tion. "By universal acceptation," he says, " Coenen- 

 chyme is the calcareous deposit originating from the 

 ccenosarc." This is most unfortunate. The word was 

 introduced by Milne-Edwards and Haime to signify the 

 common tissue which precedes the existence of the polyps 

 and plays a considerable part in their constitution. In a 

 similar sense Kdlliker uses the expression as the tissue that 

 gives rise to the axis of the precious coral. It was for the 

 soft, not the hard, parts of the " common tissue " that the 

 word was introduced. But to say that by " universal 

 acceptation " the word is used for the calcareous deposit is 

 not accurate, for the writers on Alcyonarians invariably 

 use the word to signify both hard and soft parts, other than 

 the axis, which lie between the neighbouring zooids. 



Again, the use of the word " gastro-coelom " for the 

 general body-cavity of the Coelenterate, suggesting as it does 

 a compromise with the old-fashioned gastro-vascular cavity, 

 is to be regretted. Either of the words " enterocoel " or 

 " coelenteron " is preferable. 



On the other hand, the discussion (pp. 443-4) on the use 

 of terms referring to the aspects of the coelenterate body 

 is excellent. The aspect of the body towards which the faces 

 bearing the musculature of the two complete bilateral pairs 

 of mesenteries, i, ii, are turned was called by Haddon the 

 " sulcar " aspect, and the opposite the " sulcular ■" aspect. 

 This terminology was adopted by Bourne in his " Anthozoa " 

 of Lankester's "Treatise on Zoology." Marshall, in 

 writing upon certain Alcyonarians, had previously usee! the 

 terms " abaxial " and " axial " respectively, and these 

 terms were introduced to supersede the " ventral " and 

 " dorsal " of Moseley, Kolliker, and others. It is quite 

 clear now from Mr. Duerden's remarks that the use of the 

 newer sets of terms can lead to nothing but confusion. 

 Anything that can be called a " sulcus " occurs only in 

 Alcyonaria and a few Zoantharia; the " sulculus " is a 

 myth. 



But of more importance is the fact that, as shown bv 

 Carlgren, the " sulcus " is dorsal in Cerianthus and ventral 

 in the other forms where it occurs. The axial-abaxial re- 

 lationship, moreover, is not constant. In the Alcyonaria 

 and in the majority of Zoantharia the dorsal aspect of the 

 polyp is turned towards the axis of the colony, and the 

 ventral aspect away from the axis ; but in Madrepora this 

 arrangement is reversed. In the solitary Anthozoa the use 

 of the terms " axial " and " abaxial " has no meaning. 



The conclusion is then that, although they are open to 

 some objections, the use of the terms " dorsal " and 

 " ventral " for the two aspects of the bilateral anthozoon 

 must be retained. 



In conclusion, Mr. Duerden may be congratulated on the 

 production of a really great work which marks an im- 

 portant step forward in the history of our knowledge of the 

 Coelenterata. Sydney J. Hickson. 



SEISMOLOGICAL NOTES. 

 TN No. 10, vol. ix., of the Boll. Soc. Signal. Italiana, Dr. 

 Agamennone records the fact that his idea of taking 

 photographs, at intervals, from fixed points, in regions 

 suspected of bradiseismic movements, was independently 

 suggested by F. Salmojraghi. The object is to detect slow 

 or rapid changes of relative level in the interior of a con- 

 tinent, where there is no such convenient datum level as 

 is afforded by the sea, and the paper is specially devoted to 

 showing that the effects of refraction, being irregular, would 

 not prevent the detection of a bradiseismic change of relative 

 level in a regular series of photographic records. 



No. 23 of the Mitthcilungeti of the Austrian Earthquake 

 Commission is a paper by Prof. Ldska on the application 

 of earthquake observations to the investigation of the con- 

 stitution of the interior of the earth. From a consideration 

 of the observations of the Caraccas earthquake of 



