ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 623 



base, and from them spring projections having the structure of the 

 gustatory papillae of vertebrates. In the tridactyle and buccal 

 pedicellariae the sense-cells are not collected into a sense-organ, but 

 are scattered over the surface ; and there are numerous nerve- 

 fibrils running to the epithelium. The nerve-stems consist of fibres 

 and ganglion-cells, which are more numerous at the point of branching 

 of the nerves. 



In the gemmiform pedicellariae the valves contain one or two 

 glandular sacs, with muscular walls, opening at the apex of the valve. 

 All the pedicellariae are tactile organs, as the nerve-terminations 

 indicate ; the trifoliate ones seem to remove sand and protozoa, &e., 

 from the test. The larger pedicellariae serve to keep off larger living 

 bodies, e. g. worms, and therefore act as weapons, as well as for 

 organs of attachment when the animal is moving about. 



In E. microtuberculatus the gemmiform gland-bearing pedicellariae 

 hold fast seaweeds, &c, when the animal is at rest ; these help to 

 hide it, and the secretion from the glands is therefore of the greatest 

 service. 



Striated Muscles in the Echinida-* — In reference to Dr. O. 

 Hamann's description of the striated muscles in Echinids, Mr. F. E. 

 Beddard draws attention to his own previous discovery of these 

 muscles in 1881, in Echinus sphsera. Since then Mr. Beddard has 

 found similar muscles in the pedicellariae of E. melo and E. brevi- 

 sjjinosus, Toxopneustes lividus, and in a species of Arbacia. He was 

 unable to find these elements in the Echinids from the ' Challenger,' 

 probably owing to their bad state of preservation. 



He has also found, in the above species, the peculiar structures 

 described by him and Mr. Geddes in E. sphsera; these have the 

 form of fiat plates of elastic tissue, in connection with the pedicel- 

 lariae. 



Development of Ophiopholis and Echinarachnius. f — ^ r - J- 

 Walter Fewkes finds that the larva of Ophiopholis aculeata passes 

 through a pluteus-stage ; the egg-cleavage is similar to that of other 

 Echinoderms ; a gastrula is formed by the invagination of the blasto- 

 derm, and consequently the stomach of the pluteus is an infolded 

 wall of the blastoderm, and is not formed by delamination from the 

 cells in the cavity ; the mesoderm cells originate in two lateral 

 clusters. The egg of Echinarachnius, which can be artificially 

 fertilized, segments in the same way as that of other Echinoderms; 

 it has no polar globules, while the egg is free in the water. As in 

 some other Echinoderms the gastrula is formed by invagination ; the 

 pluteus referred to Echinarachnius by A. Agassiz is an immature 

 pluteus. The mode of development of the young on the water-tube 

 of the pluteus resembles that of other Echinoids, and there is the 

 same rosette form of the water-tubes. The first formed calcareous 

 deposits of the test are trifid in shape and vary in number in different 

 specimens. The extremity of each trifid division bifurcates later 



* Ann. and Mag. Nat. Hist., xvii. (18S6) pp. 428-30. 

 t Bull. Mm. Comp. Zool., xii. (188«i) pp. 105-52 (S pis.). 



