534 



Prodromus of the 



the pedicel: the motive power of the tentacles and the 

 marginal anchors consists of a longitudinally fibrillated 

 muscular layer situated just beneath their outer wall, and 

 is directly continuous with the muscular layer in the oral 

 side of the disc : in the pedicel the muscular system is 

 cither imbedded in the gelatiniform layer, or forms longitu- 

 dinal ridges upon the inner face of it; in the former case 

 it either consists of four longitudinal cords extending from 

 the base of the pedicel, throughout its length, to the inner 

 ends of the partitions, or it forms a continuous sheath 

 subdividing the gelatiniform layer into two portions ; in 

 the latter case the four ridges* are purely muscular and 

 like the imbedded cords extend from the base of the pedi- 



1 I 



2a 2 



3 

 4a 4 



1 



2 2a 

 3 6a 



4 4a 

 6 



are ?ix tentacles, arranged as in the second diagram. No. 1 the oldest; 

 and Nos. 2, 2a, 3, 4, 4a successively younger. Bunches on each side of 

 any one partition develop in opposite spirals, as the third diagram illus- 

 trates ; « b \s the partition. In a specimen a little older than this, 

 about Tj^g- of an inch in diameter, the tentacles are ar- 

 ranged as in the fourth diagram. No. 1, the oldest, and 

 Nos. 2, 2a, 3, 4, 4a, 5, 6, 6a, successively younger, and as 

 in the last case, in opposite spirals on each side of a par- 

 tition. In this, the last, instance, it is clear that the radial 

 development, Xos. 1, 3, 5, is the same 

 in rate as tiie transverse Nos. 6a, 2a, 1, 

 2, 6, so that the tuft is about as broad 

 one way as the other. In a tuft of sev- 

 enteen tentacles of Halimocyathus pla- 

 typus, the succession is as in the fifth 

 diagram; No. 1 the oldest, and Nos. 2, 

 2a, 3, 4, 4a, 5, 6, 6a, 7, 8, 8a, 9, 9a, 10, 

 11, 12, successively, the younger ones. 

 By this it is evident at a glance that 



tiic radial development, Nos. 1, 3, 5, 7, 10, 11, 12, is far in excess over the transverse 

 Nos. 8, 2, 1, 2ft, 8a. In Carduella the transverse development is far more rapid 

 than tlie radial. Allman represents a young one with five or six tentacles in a 

 group, and all in a transverse row. Sars figures a still older one having two 

 transverse rows in each group, and four or five in each row. 



♦ In this ca<o the muscular pilasters of Lnccrnaria quadricornis are not to be 

 confounded with the i)ih»sters in the pedicel of Culvadosia, as in tlie latter they 

 are totally devoid of muscle. — See the diagnosis and description of the latter far- 

 ther along. 



