. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. CRUSTACEA. 783 plete state of doubleness ; on either side of the body we find an organ perfectly distinct, and often wholly independent of its fellow ; to such an extent, indeed, is this carried, that among the facts with which modern science has been enriched in regard to the structure of the Crus- tacea, one by no means the least interesting is that in which an animal of this class was actu- ally found presentingin either half of its body a different sex, each apparatus complete in every one of its conditions, and even
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. CRUSTACEA. 783 plete state of doubleness ; on either side of the body we find an organ perfectly distinct, and often wholly independent of its fellow ; to such an extent, indeed, is this carried, that among the facts with which modern science has been enriched in regard to the structure of the Crus- tacea, one by no means the least interesting is that in which an animal of this class was actu- ally found presentingin either half of its body a different sex, each apparatus complete in every one of its conditions, and even with the whole of its modifications.* Another fact, not less striking, is that of the analogy which exists, at least among the more perfect Crustaceans, between the male and the female reproductive organ. This similarity is so great that the simple inspection of the organ is not alone sufficient to inform us always of its true nature, which in some instances can only be ascertained by the most carefnl examination. The male apparatus consists essentially of an organ the secreting instrument of the fecunda- ting fluid, and of an excretory canal variously modified. These two parts are contained within the thorax along with nearly the whole mass of other viscera, and never extend lower down than the last ring of this region of the body. They are not always very distinct from one another, and it frequently happens that the testis and the excretory canal are confounded inextricably under the form of a single tube, nearly identical in its structure from beginning to end. The length of this canal is occasionally very great and variously convoluted and con- torted, so that its relations with the other tho- racic viscera become excessively multiplied. This peculiarity we observe very well in the Maja and the Cancer pagurus (see jig. 418). The canal, which throughout is single, is capillary at its commencement, but increases gradually in its dimensions to its termina- tion. In the Astac
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