ECHINODERMATA. 



45 



can with certainty be regarded as belonging to 

 the generative system, are the ovaries, which 

 are found in all. These animals would there- 

 fore appear to have no distinction of sex. 

 Whether the concurrence of two individuals is 

 in general necessary for propagation is uncer- 

 tain ; O. Fabricius affirms it of the star-fish, 

 but further observation would be required satis- 

 factorily to establish the fact ; he says " con- 

 greditur" (Ast. rubens) " mense Maio, oribus 

 arete connexis, altera supina."* 



a. The ovaries of Asterias seem to vary in 

 number according to the species. In A. rubens 

 and aurantiuca there are ten, two being situated 

 in each ray, above the vesicles of the feet. 

 Each of these organs consists in the former 

 species of an oblong cluster of ramified tubes, 

 (Jigs.ll and 1 6, o, and ato', cut short), proceeding 

 all from a single stem by which the organ is 

 fixed, and terminating in round vesicular dila- 

 tations. In A. aurantiaca the tubes are not 

 all connected by a single stem, but form about 

 twenty fasciculi, each of which has a distinct 

 attachment (jig. 22, o, o). 



The vesicles contain a whitish pulpy sub- 

 stance, with which they are more or less dis- 

 tended according to the season of the year; 

 so that the ovary, varying thus in size, is found 

 to occupy sometimes a greater at other times a 

 less extent of the ray, to the commencement 

 or base of which it is attached. Tiedemann 

 could discover no excretory duct of the ovary; 

 and nothing positive is known as to the way 

 in which the ova are formed and discharged 

 from the body. Tiedemann conjectures that 

 they escape by openings situate in the neigh- 

 bourhood of the mouth, in the angles between 

 the rays. 



The Ophiurahas also ten ovaries, which do 

 not lie in the rays, but in the central part of 

 the animal, and which, according to Meckel, 

 open externally by orifices on the ventral sur- 

 face. 



b. The Echinus has five ovaries, (Jig. 10, c,) 

 attached to the inside of the shell in the upper 

 part of the body, and occupying the spaces 

 between the five rows of feet. They are often 

 joined together laterally. They consist of an 

 assemblage of small round bodies, which are 

 the ova. Five short tubular oviducts come 

 from the upper end of the ovaries and open 

 externally by an equal number of orifices, 

 pierced in five oval plates which surround the 

 anus. The size of these organs, as in the star- 

 fish, varies much according to the degree of 

 maturity of the ova. The ovary, or row as it 

 is named, is the part used as food. Mr. Pen- 

 nant states that the E. esculentus is " eaten by 

 the poor in many parts of England, and by 

 the better sort abroad ;" in ancient Rome the 

 Echini formed a favourite dish at the tables of 

 the great. 



c. The ovary of Holothuria tubulosa (fg. 34, 

 w, p. 109, vol. i ) is situated at the fore part 

 of the body near the stomach and first portion 

 of the intestine. It is a tube with many clus- 

 tering branches, which terminate in blind and 



* Fauna Groenlandica, p. 368. 



slightly dilated extremities. The main tube or 

 oviduct runs forwards along the stomach, and 

 opens externally on the dorsal aspect of the 

 body a little way behind the mouth. Between 

 the insertion of its branches and its external 

 orifice, eight or ten pyriform vesicles open into 

 it, close to each other, by long tubular pedi- 

 cles. 



The size of the ovary varies excessively at 

 different periods ; its branches usually contain 

 a whitish fluid; but Tiedemann states that 

 about the end of October he has in some in- 

 stances found the organ enlarged to twice or 

 three times its usual dimensions, and con- 

 taining oblong brown-coloured bodies from 

 half a line to a line in length, which he sup- 

 poses were eggs or perhaps embryos. From a 

 statement of O. Fabricius it would appear that 

 the Hoi. pentactes is ovo-viviparous : he says, 

 " est vivipara : mense enim Martio in ilia versus 

 anum pullum libere natantem, rubicundum 

 vidi."* The pyriform vesicles are found en- 

 larged at the same time with the ovary itself, 

 and Tiedemann conjectures they may be male 

 organs, by which a fecundating fluid is produced 

 and applied to the ova. 



7. Regeneration of lost parts. The star-fish 

 affords an example of great regenerating power. 

 Individuals are often found which have evi- 

 dently sustained the loss of one or more rays, 

 and in which new rays, as yet incomplete 

 in their growth, occupy the place of the 

 old. Experiments have been even purposely 

 made which were attended with the same 

 result; but we are not aware that the process 

 of regeneration in these animals has been care- 

 fully traced in its successive steps, or at least 

 fully described. In 1741 and 42, Messrs. 

 Bernard de Jussieu, Guettard, and Gerard de 

 Villars made observations and experiments on 

 this subject at various parts of the coast of 

 France. These researches were undertaken at 

 the request of M. de Reaumur, who thus de- 

 scribes them. " They (M. de Jussieu and 

 Guettard) brought me specimens of star-fish 

 with four large rays and a small one still 

 growing; they found others with only three 

 large and two extremely small rays ; others 

 again with two large rays and three very 

 small, and, as it seemed, very young ones. 

 Lastly they more than once met with a single 

 large ray from which four small ones had 

 begun to sprout." After remarking that the 

 fact had been long familiarly known to the 

 fishermen, M. Reaumur continues, " The 

 portions into which Messrs. Jussieu and Guet- 

 tard had divided the animals appeared to go 

 on well, the wounds cicatrized and consoli- 

 dated, but the experimenters were obliged to 

 limit their stay on the coast to about fifteen 

 days ; too short a period to trace the progress 

 of a reproduction which apparently is not 

 completed till after several months, or perhaps 

 even upwards of a year."f 



BIBLIOGRAPHY. Kleinius, Naturalis dispositio 



* Fauna Groenlandica, p. 353. 

 t Reaumur, Memoires pour servir a 1'histoire 

 des insectes, tome vi. preface, page Ix. sq. 



