On the Structure of (he Stjlasteiidge. 185 



the sketching of the male gonophores of a new genus of Stylasteridae 

 {Polypora), with the stages of development of the spirmatozoa, 

 and of the female gonophores of Cryptohelia. 



Portions of the corals were preserved by means of chromic acid, 

 osmic acid, absolute alcohol, and glycerine ; and they were subse- 

 quently examined in the usual manner by means of sections. In 

 cutting the sections, a new method, described by Mihakowics, 

 'Arch, fiir mikroskopische Anatomie,' ii. Bd. 3 Hft. p. 386, was 

 adopted, and found to yield most astonishingly successful results. 

 The method seems to supply a want long felt of a means of cutting 

 tine sections of structures the parts of which are very loosely held 

 together, and where it is desirable to maintain the exact relations 

 in position of parts which in the sections often become entirely 

 disconnected from one another. Mihakowics used his method for 

 sections of vertebrate embryos ; it is certainly the best possible 

 method for the investigation of decalcified tissues, such as those of 

 Corals or Echinoderms. A strong jelly, composed of equal parts 

 of glycerine and gelatine, is used as an imbedding substance ; 

 it permeates the tissues, and takes the place of the hard calcareous 

 supporting structures which have been removed by the acid. The 

 sections are mounted in glycerine, and the imbedding substance, 

 which is left in situ in the sections, becomes perfectly trans- 

 parent, in fact almost invisible in this fluid. 1 stain the de- 

 calcified corals with carmine, then soak them in glycerine, and then 

 transfer them direct!)' to the warm fluid jelly, instead of treating 

 them first with absolute alcohol after staining, as does Mihakowics. 

 A teaspoon heated in hot water is a most convenient instrument 

 for transferring the small masses of tissue, with the fluid jelly, 

 to the cavities in the hardened liver used as an imbedding base. 

 I have dwelt upon this method because it seems to me likely to 

 be one which will prove of the greatest service in all kinds of 

 difficult histological problems, such as Corti's organ, early stages of 

 embryos, retina, &c. It is quite possible by the method to obtain 

 sections of a single hydroid sporosac or planula. 



The Stylasteridae obtained ofl: the Eio de la Plata comprised six 

 genera, viz. : — Stylaster ; Cryptohelia ; Allopora ; Errina ; a nev^ 

 genus, Polypora ; and a further new genus allied to Errina, 

 which I propose to term Acantliopora. There is much confu- 

 sion as to the determination of even the genera of the Stylas- 

 teridae, and I have found it impossible to determine species in 

 the absence of specimens for comparison. The Stylaster appears 

 probably to be S. eriibescens of Pourtales*. The Cryptohelia 

 is the same as that obtained all over the world by the ' Chal- 

 lenger' in deep water, and apparently not specifically distinct 

 from C. pudica t. Of the Allopora I cannot determine the 



* Illustrated Catalogue of tbe Museum of Comparative Zoology at Harvard 

 College. No. IV. Deep-Sea Corals. By L. F. de Pourtales. Cambridge, Mass. 

 1871, p. 34. 



t Hist. Nat. des Coralliaires, par MM. Milne-Edwards et J. Haime, t. ii,, 

 p. 127. 



Ann. & Mag. N. Hist. Ser. 4. Vol.xix. 13 



