THE HYDBOSPIBES A\l> BPIBA0LB8. 85 



incuts concerning the latter 1 . '"It represents u membranaceous sack of peculiar 

 construction, as it cannot very well be of calcareous Lamellae, admitting Hillings' 

 definition to be a correct one" (i.e. that the ambulacra are respiratory organs), 

 llumbach gives no details concerning the peculiar construction <>l' the hydrospire-sac ; 



but we do not think that he would have had much doubt as to the calcareous nature 

 of its Avails if he had seen the specimens represented in PI. X. tigs. 13, 14, the first 

 of which had already been figured by Rofe. Hambach goes on to describe the plica- 

 tion of the inner face of each hydrospire-sac and says that " these foldings are so 

 arranged that they represent an unsymmetrical figure 8, of which the upper loop is 

 larger than the lower one .... In such well-preserved specimens we may also 

 observe that the upper loop of the plications surrounds, or that the cavity produced 

 by these folds is filled out by, a tube, which I suppose to be the ovarian tube, and 

 which has its outlet through the ten openings surrounding the anuulus centralis; 

 explaining, on the other hand, the necessity of the grooves for the support of the 

 hydrospiric plication, which by this arrangement are kept from obstructing the free 

 passage of the ovulum." 



We have had some difficulty in understanding from the above description where 

 Mr. Hambach believes the ovarian tubes to have been lodged ; but from what he 

 says in his subsequent paper " about the only space which could have been occupied 

 by them being " below the hydrospiric sac and between the plicas," we conclude that 

 he imagines every two of the lamellar tubes of each hydrospire-sac to have been 

 separated by an ovarian tube which was outside the hydrospire-sac altogether and 

 contained within the body-cavity. Thus, for example, there would have been six 

 ovarian tubes on each side in Pentremites pyriformis (PI. XVIII. fig. 3), three in 

 P. conoideus (PI. XVIII. fig. 0), two in Mesoblastus elongatus and M. angulatus 

 (PL XVII. figs. 9, 10), and one in Granatocrinus Norwoodi and Elceacrinus Verneuili 

 (PI. XVII. figs. 8, 19). But what was the position of the ovarian tube in forms like 

 Granatocrinus campanulatus, G. Deriiensis, G. ellipticus, G. orbicularis, and Schizo- 

 blastus Mofei (PI. XVII. figs. 2-7), in which there is but one hydrospire-tube on each 

 side of the ambulacrum \ For the hydrospire-sac is devoid of any " plicas," and has 

 simple straight walls without any " upper loop " which could have been occupied by 

 an ovarian tube. 



We likewise fail altogether to understand how the ovarian tubes of Pentremites 

 piriformis could have communicated with the exterior through the spiracles if they 

 were situated below the hydrospire-sac, as Hambach describes. The spiracles do not 

 lead into the body-cavity at all, but only into the hydrospire-sac (PI. I. figs. 6, 7 ; 

 PI. X. fig. 14; PI. XII. fig. 13), and cannot therefore have communicated with 



1 Trans. St. Louis Acad. Sci. 1880, vol. iv. no. 1, p. 152. 

 - Ibid. 1884, vol. iv. no. 3, p. 542. 



