74 S. LOVEN, ON POUKTALESIA, A GKNUS OF ECHINOIDEA. 



A due attention paid to the development of parts during the growth of the indivi- 

 dual animal has more than once reconciled discrepancies as great as that of the cal)'- 

 cinal system in the Ethmophracti and the Ethmolysii, the Mesozoic type and the Cenozoic. 



In the young of Abatus cavernosus, PL XIV, fig. 164, 164 A, the calycinal sy- 

 stem, relatively large, presents iive radials I, II, III, IV, V, each bearing a tentacle, 

 and four costals, 1, 2, 3, 4, among which the 2 has become already the site 

 of the niadreporite. The central and open part is overlaid, within the general enve- 

 lope, by a membrane in which are seen detached minute calcified lamina», presumably 

 rudiments of the central ossicle and the costal 5, nowhere extant among the Ethmo- 

 phracti, but here to be developed, PI. XVIII, fig. 220. after the backward passage of 

 the excretoi'y end of the alimentary tube. 



Young Spatangi, with the mouth and tlie vent opened, and living free on the 

 bottom of the sea, very early present a calycinal system comj)leted by the presence of 

 the central disk and the costal 5. Different stages of Echinocardium flavescens 0. F. 

 MuLLEK, Spatangus purpureus 0. F. M., and Brissopsis lyrifera Forbes, PI. XVII, XVllI, 

 XIX, may serve as examples showing the development of the calycinal system and 

 the movement of the madreporic apparatus in the Spatangida; Ethmolysii. Of the first- 

 named the calycinal system is represented PL XVII, fig. 197 — 207, as it appears in 

 specimens of different dimensions, from mm. ;-),r. : 3 to mm. 36 : 32. In the Aoungest 

 the five radials are present Avith tlieir ocular ijures. The whole system, up to the in- 

 dividual size of mm. 30 : 26, is more or less distinctly pentagonal. The central ossicle 

 together with costals 2, 3, 5 are united into one continuous middle area, extending 

 through the whole length of the system, with the radial III in front, the ra- 

 dials IV and V and costal 4 on the left, and radials I and II togetlier with costal 1 

 on the right. At first, fig. 197 , 198, the niadreporite is a single pore placed nearly in 

 front, then there are two or three pores, /z/;. 199 — 205, of Avhich the last added is more 

 towards the middle; in a specimen of mm. 14,5:12, /z^. 203, out of five pores tAvo 

 are posterior. Meanwhile the costals, at the total size of mm. 10,5 : 9 and mm. 12 : 10, 

 fig. 203, 204, have been provided with sexual pores, at first so minute as easily to be 

 taken for madreporic pores, but becoming larger according as the reproductive organs 

 are developed. At mm. 30 : 26, fig. 206, the swarm of madreporic pores lies more 

 than half behind the middle, and at mm. 30 : 32, fig. 207, nearly the Avhole of it be- 

 hind the costals 1 and 4, and the costal 5 has been driven backward into the inter- 

 radium 5; but still its intact margin is seen to limit the pressure of the p(n-es. And 

 during this transference, in this species as in those next to be described, the middle 

 part, expanded as long as occupied b}' the growing niadreporite, contracts again when 

 it has passed, yielding to the pressure exerted l)y the interradia. 



A series of young stages of Spatangus purpureus 0. F. M., from mm. 5 : 4 to mm. 

 24:21, presents similar modifications, PL XVIII. fig. 209—219. There is the same 

 drawing together of the sexual openings and narrowing of the middle area, after the 

 recession of the madreporic filter, which is richer in pores than that of Echinocardium, 

 and much more expansive, so much so as largel}' to invade, at mm. 53 : 50, the costals 

 1 and 4, to fill to the very brim the costal 5, stretching it to the utmost and leaving no 



