<^ 97. THE ECHINODERMATA. 97 



the shell, filling the empty spaces between the double rows of ambulacral 

 vesicles. 



They consist of widely ramified, deeply interlocked coeca, having always 

 proper excretory ducts, which open upon the genital plates of the back of 

 the shell. ^^'^ There are here always five of these organs, and the genital 

 plates, alteniating with the ocellary ones, surround the anus.*'*'' In some, 

 species of the Clypeastridae, and Spatangidae, there are, perhaps, only four 

 of these organs, judging from that number of the plates. *''^' In the Holo- 

 thurinae, these organs have a very different arrangement. They consist of 

 widely-branched coeca, *'''^> floating, as loose clusters, freely in the cavity of 

 the body, and opening through a single common -excretory duct, situated 

 below the osseous circle, and between the oral tentacles. 



The testicle, which is of a whitish color, consists of a cluster of cj'lindri- 

 cal sacs, branched and interlocked with each other.*'**' But the ovary is 

 pale red, very long, branched, a little flattened, and extends even to the 

 posterior end of the body.*-"' 



As the only exception among these animals, the Synaptinae are her- 

 maphrodites. But it should be stated that we know of them only through 

 Synapta Diivernaea. It is said that here the testicles and ovaries are 

 united in one and the same organ.*-'' Three or four long cylindrical sacs 

 float in the cavity of the body, and have an excretory duct which opens 

 back of the osseous circle. At the epoch of procreation, vesicular pro- 

 longations appear on their interior surface, in which are formed spermatic 

 particles. The spaces between these prolongations are filled by a pultace- 

 ous mass, in which appear eggs.*--' 



In the Sipunculidae, and Echiuridae, there are only two or four simple 

 cylindrical contractile pouches attached to the ventral wall. It is yet 

 undetermined whether their contents escape by rupture, or through special 

 openings. *^''' 



15 The separate sexes of Echinus were first is snmethiii;; so remarkable, that one cannot but 



shown by Peters ; see Muller''s Arch. 1840, p. believe that Quatrpfa^es has here taken the 



143. parent sperm cells for the Cfrgs. 



IG See Tiedemann, Inc. cit. p. 85, Taf. X. fig. 1, ^3 In Sipunculus, and FhaHcolosoma, there is 



4, 8 ; and especially t^alentin, Monogr. &c. p. 103j observed on eaoli side, a little front of the anus, a 



PI. VIII. sac attached t) the side of the body (see Delle 



'i~ '\\"\t\iEchinanthus,Mellita,Rotula,Scutella Chioje, loc. cit. Tav. I. fig. 5, s. s. and Grube, 



(see Agassiz. Monogr. des Scutelles), and Spa- 3IiUler's Arohiv. 1837, Taf. XI. fig. 1. v"). 

 tanifus arcuarius, and ovatus, I can count only These have been regarded as genital organs. In 



four genital plates, while in Encope, and Clijpecis- Sipunculus nudns, Grube has found eggs not 



ter, I find five ; yet yalentin (Repertorium, 1840, only in these sacs, but in the cavity of the body 



)). 301) expressly speaks of five genital organs in also. It may, therefore, be <iuestioncd if the eggs 



SpatariKus violaceus. escape from the sacs into the cavity of the body, 



i>* Wairner and raleniin were the first who whence they arc expelled through an opening at its 



noticed the sexvial differences of Holothuria tuba- posterior extremity, or if they are accidentally 



Insa; see Froriep''s neue Not. No. 240, p. 90. introduced from without with the water, during 



19 See Wagner, Icon. zoot. Tab. XXXII. fig. 11 respiration. In this last case, these sacs should 

 (Holot/iuria tubulosn). I have already remarked have excretory ducts; and there arc, indeed, in 

 (§ 86), that the white cylindrical pedicelte, taken Sipunculus nudu.i, two external !bss;e opp<isite 

 by some zootoraists as testicles (Delle Chiaje, loc. the point of insertion of the sacs (see JJe'lc 

 cit. I. p. 97, Tav. VIII. fig. 1. o.), are distinct from Chiaje, loc. cit. Tav. I. fig. 2, f.), and in which, it 

 the genital organs, and communicate directly with is said, there are two very sm:vll openings. Ac- 

 the intestinal canal. cording to Forbes and Goodsir, the genital sacs 



20 See the Catalogue of the Physiol. Series, &c., of the male Echiurus vulgaris contain a seminal 

 loc. cit. IV. PI. XLIX. fig. 1. c. {Holothuria tub- liquid, with very active spermatic particles, while 

 ulosa). those of the female are filled with eggs ; see Fro- 



21 Quatrefages, Ann. d. Sc. Nat. loc. cit. p. 66, riep's neue Not. loc. cit. p. 281, fig. 20, 22, 12, 

 PI. IV. fig. 1, q. PI. V. fig. 1. f. f.* 



22 This deep confusion of the organs of two sexes 



* [§ 97, note 23.] For the sexual organs of Sipunculus, see Peters {Mailer's Arch. 1850, p. 



9 



