MOLLUSCA. 39 



the penis, opens at its end. A black bristle has been placed 

 under the two ducts. 



The ovaria are disposed in the peduncle and in the body. 

 In the peduncle they may be seen as a tangled mass 

 of branching tubes, filled with granular matter and immature 

 ova. From the peduncle two main ducts (not seen in this 

 specimen), one on each side, enter the body at the anterior 

 corner of the rostrum, whence they curve round towards the 

 base of the first pair of cirri. There they form two glandular 

 masses resting on the upper edge of the stomach, of an orange 

 colour, and generally subdivided near the mouth. These masses 

 were thought by Cuvier to be salivary glands, but are now 

 known to be true ovaries. No proper oviduct has yet been dis- 

 covered. In the uppermost of the two specimens, between the 

 body of the animal and the peduncle may be seen one of the 

 ovigerous lamellae in which the ova exist previous to their ex- 

 pulsion. 



Darwin, " Monograph on the Cirripedia," p. 55, sq. 



SUB-KINGDOM MOLLUSCA. 



Division I. MOLLUSCOIDEA. 

 Class TUNICATA. 



In the following preparations of Ascidians a Hue rod has 

 been placed in the inhalent, a red rod in the exhalent, aperture. 

 Eolleston, p. 66. 



57. A simple Ascidian (Cynthia microcosmus.) 



One half of the test, which in this species is of a leathery 

 consistency, has been removed, to shew the animal suspended 

 within it. The mantle is attached to the test at the two aper- 

 tures, and is very muscular. Fibres may be seen passing in a 

 longitudinal, oblique and transverse direction across its surface. 

 The two apertures are regarded by some as homologous with 

 the inhalent and exhalent siphons of the Siphonate Lamelli- 

 branchiates; and by others, as the mouth and anus. 



58. One-half of the test, mantle, and branchial sac has been 

 removed, so as to expose the cavity of the latter. The branchial 



