HicKsoN — Notes on a Small Collection of Kydrocorallince: 507 



calcareous pieces composing the coenosteum or hard parts of the 

 colony (calc). In decalcified preparations the mesogloea is always 

 very considerably shrunk, so that it is not easy to make out very 

 clearly its histological structure. In sections prepared by Von 

 Koch's method of grinding down together the hard and soft parts 

 in solid Canada balsam rather more satisfactory results can be 

 obtained, but the true nature of this interesting tissue will only 

 be understood when macerated and teased preparations are made 

 from living specimens. As I have not yet done this I can only 

 make a few remarks on the structure of the mesogloea as it 

 appears in my sections of spirit specimens. 



In the first place it must be remarked that we have in Disti- 

 ihopora a much more extensive mesogloea than in Millepom. The 

 skeleton, moreover, is not in close contact with the cells of ecto- 

 derm in the deep parts of the corallum, but lies embedded in the 

 mesogloea as is represented in fig. 22 on Plate xxx. {I.e.) . In Mille- 

 2)ora, on the other hand, the mesogloea is represented by a very thin 

 perfectly structureless lamella situated between the ectoderm and 

 endoderm, and the skeleton lies in all cases outside the ectoderm in 

 close contact with its cells. The mesogloea of Didichoijora always 

 stains very deeply in borax- carmine, and hsematoxylin ; it contains 

 a few very small scattered nuclei and a number of lines running 

 in all directions through its substance, which are probably the 

 result of the shrinkage produced by treatment in acid and alcohol. 



In Stylader the relations of the coenosteum to the mesogloea 

 seems to resemble that of Distichojoora, but it will be necessary to 

 examine more and larger specimens than have been at my disposal 

 before this point can be definitely settled. In Allojjora there is no 

 doubt that superficially the coenosteum bears the same relation to 

 the ectoderm that it does in Millejjora, as I have correctly shown 

 in my paper on the development of this form ; but a re- exami- 

 nation of my sections shows that in the deeper parts the ectoderm 

 layer disappears and the coenosteum lies buried in a mesogloea 

 similar to that of Distichopora. 



Millepora Murrayi, Quelch. 



Since the publication of my last paper in the Quarterly Journal 

 of Microscopical Science I have received from Professor Haddon 

 some more dried specimens of the Millepora from Torres Straits, and 



