Microscopic Journal, and Structural Record . ications of which termi-nate in Cceca. Mr. Bower-bank has ascertained thatthese vessels are not imbeddedin the substance of the fibreitself; but, are enclosed inan external membrane or sheath, covering the sohd fibre. In some of the vessels Mr. B. observed numerous small globules,somewhat analogous to those of the blood of the higher animals ofa circular form, and varying in diameter from the y^.V^th to the L th of an inch. The mean diameter of the vessel was the ^B-th 5 O > 0 0 0 of an inch, and the diameter of the fibre on which the vessel
Microscopic Journal, and Structural Record . ications of which termi-nate in Cceca. Mr. Bower-bank has ascertained thatthese vessels are not imbeddedin the substance of the fibreitself; but, are enclosed inan external membrane or sheath, covering the sohd fibre. In some of the vessels Mr. B. observed numerous small globules,somewhat analogous to those of the blood of the higher animals ofa circular form, and varying in diameter from the y^.V^th to the L th of an inch. The mean diameter of the vessel was the ^B-th 5 O > 0 0 0 of an inch, and the diameter of the fibre on which the vessel anasto-mosed measured yfg-th of an inch. This structure is not confined tothe Turkey species, but has also been observed by the author on manyof the Australian sponges. The only true tubular recent sponge known to Mr. B. is the Spongiafistularis as described by Dr. Grant, specimens of which he has satis-factorily examined, and which he proposes to separate from this group,and has suggested the generic name of Fistularia. This separation is. MICROSCOPIC MKASUREMKNT. 11 considered by the author to be the more necessary as tubular speciesare not uncommon among fossil sponges. Mr. B. also made some observations on the nature and structure ofthe spicula. He cannot reconcile himself to the descriptioa given byDr. Grant: viz. they appear to be tubular like many natural crys-tals, as he is not aware of the existence of true cylinders in crystal-line bodies, such as the silicious and calcareous sponges can he agree with Professor Rymer Jones on the identity ofthese with the raphides or crystals formed in the cells of plants ;these bodies are solid, and in no case cylindrical, they are mereadventitious bodies in the vegetable kingdom ; and cannot, therefore,be compared with the spicula which occur in sponges, forming a portionof the organization of the animal. The normal form of either kinds ofspicula Mr. B. considers to be always the same, another proof of theiranimal d
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