44 Mr. T. Higgin on the Structure of the 



It is the same witli the septa of the polypary. The number 

 12 is lirst of all produced, but with this difference, that the 12 

 elements all begin to show themselves at the same moment ; 

 and it is only later on that their unequal growth ranges them 

 in two groups which appear to be of different age, whereas 

 they are only of different sizes. 



The facts here brought forward appear to us to be of absolute 

 certainty. They have been repeatedly conlirmed, sometimes 

 upon polypes taken swimming in the sea in the form of the 

 embryonic sphere without any divisions, and brought up until 

 the complete formation of their polypary, which was affixed to 

 the walls of the microscopic cells in which they were kept for 

 observation, which enabled us to follow under the microscope 

 a single embryo, of which the origin of the parts and the forma- 

 tion of the framework might thus be watched — and sometimes 

 also upon very young individuals collected on the rocks of 

 the localities inhabited by Astroides or Balanojphyllue. 



VIII. — 0)1 the Structure of the Skeleton q/Euplectella asper- 

 gillum. By Thomas Higgin, Member of the Liverpool 

 Microscopical Society. (In a Letter to T. J. MoORE, Curator 

 of the Free Public Museum, Liverpool.) 



[Plate III.] 



[The specimen referred to in the following paper is one of 

 two examples purchased of Mr. Gealein November 1866. It 

 is 12 inches in length measured along the outer curve, and of 

 a very uniform diameter of 1 inch. The other specimen is 

 somewhat longer and stouter. Both are in a more natural 

 condition than is seen in the examples usually submitted for 

 sale ; and both are of a pale brown colour. The smaller spe- 

 cimen is somewhat compressed towards the top, perhaps owing 

 to pressm'e while drying; and nearly half the lid-like top is 

 torn away, leaving a jagged edge, marring the beauty of the 

 specimen. The lower third of the sponge is rigid, the rest 

 soft and yielding throughout, the rigidity extending some- 

 what higher upon the inner than on the outer side of the curve. 

 It is,* as Mr. Higgin supposes, the specimen referred to by 

 Prof. Wyville Thomson in his " Letters from II. M.S. Chal- 

 lenger," published in ' Good Words ' for July 1873, p. 510. 

 On passing through Liverpool to Belfast in December 1868, 

 he paid a hurried visit to the Museum, saw both examples, 

 and I gave him a fragment from the smaller one for use 

 under the microscope. It is remarkable tliat all the specimens 



