SEXUAL ORGAXS OF TUNICATA. 407 



dicularlte have no efferent ducts for tlieir sexual glands, which are 

 sometimes paired and sometimes single. In the Acopa the sexual 

 elements are discharged into the cloaca. The male organ has the 

 form of a sperm-producing Ccecum, which in Doliolum, and also in 

 many Ascidians, retains this simple form ; whilst in Pyrosoma it 

 acquires a rosette-like shape, and in most Ascidians, and also in the 

 SalpEe, is produced into branches, and forms a kind of multilobular 

 gland. In many Ascidians (Molgula) the testes surround each of 

 the two ovaries as a number of separate glands, and open to the 

 exterior with separate efferent ducts. The ovaries too have often a 

 multiiid character, at least in many Ascidians ; in others they are 

 only represented by a group of eggs of different stages of develop- 

 ment, each of which is enclosed in a kind of capsule. In many only 

 a few such eggs, joined together by a common stalk, are present ; 

 and in the Salpte and Pyi'osoma we have only a single egg, the stalk 

 of which exists in the early stages of growth, but gradually shortens. 

 The development of the sexual products occurs here at different 

 periods for the two sexes ; the male organ only reaches its maturity 

 after the egg has commenced to develop as an embryo. 



The presence of an efferent duct for the sexual products appears 

 to depend upon the greater or less distance of the sexual glands 

 from the cloaca. The whole apparatus, however, requires a very 

 much more careful investigation than it has yet received. 



