ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 411 



pores in single linear series ; the separation of the gastropore and dactylo- 

 pore systems is a further distinctive feature. 



Coral Studies.* — Dr. A. E. v. Heider is led by the study of Astroides 

 calycularis and Dendrophyllia ramea to some general considerations as to 

 the structure of corals. He is firmly convinced of the presence in intact 

 living corals of an outer soft investment to the theca ; in colonial forms 

 the body-walls of the polyp very soon pass into the Cfenosarc which con- 

 nects the separate individuals, and then the investing part becomes very 

 hard to detect. In the solitary form it is otherwise, and in DendropliylUa, 

 for example, the outer investment is often considerably longer than the 

 polyp. This outer thecal covering or marginal plate, has not the same 

 composition in all corals ; in Gladocera, BendrophylUa, &c., all the three layers 

 are present ; but in Astroides and Flabellum (according to Prof. Moseley) 

 the outer surface of the skeleton is formed directly of a simple layer of 

 meso- and ectoderm, and there is no continuation of the body-cavity between 

 the theca and the body-wall. 



It is, morphologically, a very important fact that in one group of corals 

 which, according to present systematic arrangements, consists of members of 

 yarious families, the theca is formed quite independently of the body-wall, 

 and that in another group the body-wall takes up the theca into its 

 mesodermal layer. If this generalization be correct we have two divisions 

 of Madreporaria : that of the Euthecalia in which the body-wall secretes 

 calcareous substances within its mesodermal lamella, and forms an 

 " eutheca" which ultimately becomes connected with the septa; and that of the 

 Pseudothecalia, in which the body remains connected with its three layers 

 and secretes no theca, but in which the septa become connected by cal- 

 careous substance at their peripheral ends, and so form a " pseudotheca," 

 outside which is the continuation of the body-cavity. In skeletons de- 

 prived of their soft parts it is, of course, difficult, or even impossible, to 

 determine how the theca has been formed ; the author is inclined to think 

 that well-developed costae are associated with a pseudotheca. 



It would appear that the ectodermal layer of the young polyp which 

 excretes the calcareous matter is completely surrounded in time by the 

 mesoderm ; the author does not agree with Dr. von Koch in thinking that 

 the cells persist and excrete lime, but that they are converted into it, and 

 that, therefore, they cease to exist as cells. 



Anatomy of Fungia.j — Mr. G. C. Bourne describes the arrangement 

 of the tentacles and septa, which is very regular in Fungia, and not irregular, 

 as has previously been supposed. Prof. Duncan's doubt whether there were 

 any mesenteries is shown to be unfounded, and indeed, they have all the 

 essential characters of the mesenteries typical of Hexactinian Actiniaria ; 

 seven orders correspond to the seven orders of septa. There are no 

 synapticulsB in the upper portions of the interseptal loculi, where the 

 mesenteries are free to radiate across the whole space between the mouth 

 and the periphery of the disc ; here then is the ordinary central structure- 

 less supporting lamina which the author proposes to call the mesogloea — 

 this new term being the equivalent of the German " Gallertlage" — of which 

 the bodies of Medusse are for the most part made up. 



The coelenteron is represented by the axial space lying below the stomo- 

 dseum, the peripheral chambers known as exocoeles and endocoeles, and the 

 space which lies between the theca and the outer body- wall ; the compli- 

 cated relations of their parts only seem to be explicable on the theory of 



* Zeitschr. f. Wiss. Zoo]., xliv. (1886) pp. 507-35 (2 pis.), 

 t Quart. Journ. Micr. Sci., xxvii. (1887) pp. 293-321 (3 pis.). 



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