738 KECORD OF CURRENT RESEARCHES RELATING TO 



shields adambulacral pieces, and the second ventral shields subambu- 

 lacral; and it is concluded that the whole of the oral skeleton is 

 formed by tlie conversion of the first two joints of all the five rays, 

 together with the adambulacral and subambulacral pieces which belong 

 to these parts. 



As to the generative organs, of which so little is exactly known, 

 it is generally stated that, in the Ophiurida, the generative pro- 

 ducts are passed into the coelom, and thence escape by the so-called 

 genital clefts, but it is here shown that the generative products do not 

 take this course, and that the genital clefts do not open into the 

 coelom. After a review of what has been stated by earlier writers, 

 Dr. Ludwig draws attention to the description he gave when treating 

 of the Asterida, when he showed that the genital clefts open into 

 depressions of the body-wall, for which he proposed the name of 

 hursce genitales, while the clefts were named " bursal clefts." An 

 examination of OpMoglypha shows that in it the bursa is a compara- 

 tively wide, but very thin sac, which commences at the edge of the 

 bursal cleft, and passes dorsally into the coelom ; at its aboral end it 

 is continued into a narrower portion which passes over the edges of 

 the stomachal sac towards its dorsal aspect ; it is a mere invagination of 

 the integument. The genital tubes are placed on that surface of the 

 bursa which faces the coelom, and the large number of fifty has been 

 counted on each bursa ; in youth they are rounded, but they gradually 

 take on a cylindrical form ; internally they are invested by a spermi- 

 genous or ovigerous epithelium, and the outer lamella of their walls 

 is provided with muscular fibres, somewhat irregulai'ly arranged ; in 

 general structui'e tbey resemble the similar organs of the Crinoida, 

 Asteroida, and Holothuroida. The generative pores may be seen to 

 form a number of small orifices, surrounded by epithelium, separated 

 by regular distances, and leading directly into the cavity of the genital 

 tubes, which are connected with them by very short efierent ducts ; 

 the contents are thus passed, not into tlie ccelom, but into the bursa. 

 Having compared the arrangements in various Ophiurids, the author 

 points out that in them, just as in the case of the branchial vessels of 

 the Asterida, there is reason for supposing that the burste serve also as 

 respiratory organs, and suggests that they may also serve as marsupial 

 pouches. That many Ophiurids are viviparous is certain, and the 

 suggestion is one which would free us from numerous difficulties. 

 The paper, which is of great value, concludes with pointing out ^the 

 likenesses that subsist between these burste found, among extant 

 Echinoderms, in the Ophiurida only, and the " genital tubes " or 

 " hydrospira " of the Blastoidea. 



Aspidura.* — Dr. Ludwig has some interesting remarks on Dr. 

 Pohlig's late paper on this Triassic Ophiurid,| in which it was stated 

 that the oral shields were divided into two equal lateral parts. 

 Striking as this relation is, it was explained by the apparently justi- 

 fiable supposition that the oral shields (" buccal plates ") are primi- 

 tively paired, owing to their origin from the lateral plates of the 



* ' Zool. Anzciger,' ii. (1879) p. 41. f I'liis Journal, ii. p. 581. 



