§ 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, alternating 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 cylindri- 

 cal sacs, branched and interlocked with each other. ^^^' But the ovary ie 

 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 bodj^, 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 something so remarkable, that one cannot but 



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



143. parent sperm cells for the eggs. 



Ii5 See Tiedemann, Ion. cit. p. 85, Taf. X. fig. 1, -3 In Sipvnculus, and Phascolosoma, there is 



4, 8 ; and especially Valentin, Monogr. &c. p. 103, observed on each side, a little front of the anus, a 



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



IT "With Echinanthus, Mellita, Rotiila, Scutella Cfiiaje, loc. cit. Tav. I. fig. 5, s. s. and Grube, 



(see A^nxsiz. Monogr. des Scutelles), and Spa- Mailer's Archiv. 1837, Taf. XI. fig. 1. V). 



tan^us arcuarius, And ovatiis,! can count only These have been regarded as genital organs. In 



four genital plates, while in E7!co/;e, and C/(/^pas- Sipunculus 7iudas, Grube has found eggs not 



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



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



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



^i Warner and Valentin were the first who whence they are expelled through an opening at its 



noticed the sexnial diflftrences of Holothiiria tuba- posterior extremity, or if they are accidentally 



losa ; see Froriep's neue Not. No. 249, p. 99. introduced from without with the water, during 



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



{Holothuria tubulosa). I have already remarked have excretory ducts ; and there are, indeed, in 



(§ 86), that the white cylindrical pedicellse, taken Sipunculus nudus, two external fossas opposite 



by some zootomists as testicles (Delle Chiaje, loc. the point of insertion of the sacs (see Delle 



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 du-ectly with is said, there are two very small openings. Ac- 



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



:iO 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 Fr»- 



^I 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 (Maller^s Arch. 1850, p. 



9 



