COMPOUND ASCIDIA. 161 



and a half in length. These living animals are confined to the surface of 

 the mass, which, distended by the vigour derived from a salubrious con- 

 dition, is partly translucent. 



The mass is solid. Its interior consists of a clear, consistent, trans- 

 parent, greenish, gelatinous substance, interspersed with a peculiar orga- 

 nization, fig. 15. Observations on the preceding subject gradually in- 

 creasing, shews this, which is deep-seated, to be the sanguiferous system. 



Perpetuation. — The most profound physiologists maintain that the true 

 analogy of animal kindred, must be sought from reciprocal corespondence 

 of their earliest formation. 



An admirable demonstration was presented here. 



Some days posterior to the acquisition of the large specimen just de- 

 scribed, dull orange corpuscula were perceptible amidst its flesh, which 

 afterwards rising nearer the surface, became more conspicuous. 



A smaller vessel was next introduced under the specimen, wherein 

 twelve or fifteen yellow ova or capsules were soon after discovered amidst 

 the muddy pellets falling below. 



Subjected to the microscope these were found of ovoidal form ; the 

 first inspected exhibiting a solid nucleus, invested by a transparent integu- 

 ment, and others had nearly the same character. — Fig. 16. 



But some being examined which were farther advanced, exposed a 

 spinula confined within a diaphanous membrane, the head forming the 

 darker nucleus, surrounded by the curving tail. It forcibly reminded me 

 of the appearance of the embryo skate on slitting up the capsule, which may 

 be seen in all stages of imperfection early in spring, and during the summer 

 season. By gradual progress the tail of the spinula, here unfolding in 

 curvature, fig. 16 b, extends straight to complete the animal's shape, and 

 the head is shewn as equal to about a fourth of the whole length. 



In eight or nine hours after introduction of the small vessel, not fewer 

 than an hundred yellow corpuscula had been discharged into it. A num- 

 ber distinguished as of roundish or long oval form lay motionless below ; 

 and many having attained complete evolution of the parts as spinula?, were 

 swimming actively six inches above the bottom of the large vessel con- 

 taining the small one. — Fig. 17. 



VOL. II. x 



