2g LUCERNARI^ AND THEIR ALLIES. 



sections on organography (Ch. V), and we shall, therefore, confine ourselves to 

 layin" down their topographical status and their relations to the sites of the 

 other or'^ans. This we have in part anticipated when describing the caudal 

 compartments, but considering the importance of their morphological features, we 

 need not hesitate to repeat what we have said concerning the muscles, especially as 

 the subject matter will be viewed from another stand-point. In tlie paragraph (53) 

 upon the posterior division of the main cavity, four low longitudinal ridges were 

 described as trending along its inner face and finally disappearing near its junction 

 with the caudal channels. Tliese ridges {fios. 37, 50, r'-) are the muscular cords, 

 which, in this region, come to the surface as they pass forward from the pedicel 

 into the umbella. In a transverse section of the peduncle it will be observed that 

 they appear as triangular bodies {fig. 52, r) which lie nearer to the surface than to 

 the axis, and exactly half-way between the canals. At the extreme posterior end 

 of the peduncle they expand rather abruptly into a sort of truncate brusli {fig. 

 37, /), and bending there, at a riglit angle, extend along the inner face of the 

 adherent disk to tlie axial line, still buried, however, in the gelatiniform layer 

 {fig. 19, /). Passing forward, each one keeps its place midway between the 

 canals, and pretty near the exterior at first, but, at the anterior third of the 

 peduncle, swerves from this course, and gradually approximates the axial line, and 

 finally strikes the surface of the posterior division of the main cavity a sliort 

 distance in front of the entrances to the peduncular channels. Here it is that 

 they begin to rise above the level of the parietes of the cavity, and extend, with 

 rapidly decreasing diameter, in the form of low ridges {figs. 37, 47*, 50, r") (^ 53), 

 to the proximal ends of the partitions. At these four points each one enters a 

 partition {■^") and passes forward very obliquely {fig. 47*, r^ to i^'') toward the 

 outer surface of the anterior or circumoral face of the umbella, and there expands 

 into a thin stratum (?«') just beneath the superficial layer of cells. These then are 

 the only points where the muscular layer of the umbella {^ 44) is united with that 

 part of the system which is in the peduncle. It is at these points, also, that the 

 muscular layer of the proboscis {fig. 47% m") is connected with the cords. 



CHAPTER V. 



ORGANOGRAPHY. 



§ 10. TJie Walls. 

 60. The nomenclature of the various regions of an Acalepli is as yet in its infancy, 

 and particularly so in regard to the strata of cells or of substances of other forms 

 which constitute the solid parts of tlfc body. Huxley and Allman^ were the earliest 



' See Huxley in Phil. Trans. Roy. Soc, 1849, and -Oceanic Hydrozoa," in Roy. Soc Pub., 1859. 

 Also Allman, Anat. Conhjlophora, Phil. Trans., 1853, and Report Brit. Assoc, for 1863. 



