AND PHYSIOLOGY OF THE TUNICATA. 319 



occupies the centre of the left side of this tunic. The oviducts 

 are two short tubes ; they pass out of the ventral or anterior 

 extremity of the mass, and open into the cloaca on each side of 

 the intestine. There are four or five long nipple-like sperm-out- 

 lets, situated at a little distance from each other along the body 

 of the organ. These open directly into the atrial space on either 

 side of the branchial sac. 



A similar arrangement of the genitalia, with numerous short 

 deferent canals, has been described by Yan Beneden, in his 

 Ascidia ampulloides*, which is, there can be little doubt, a Mol- 

 gula. There are two similar genital masses in M. simplex ; but 

 they are comparatively slender, and are pretty regularly fusiform ; 

 they are situated exactly in the same way as those in the former 

 species ; but that on the right side is overlapped by the looped 

 portion of the intestine. 



In an undescribed species obtained by the Eev. A. M. Norman 

 in Gruernsey, the genital masses are ovate, and are placed as 

 usual, but differ from those of all other species in having the 

 oviducts passing from their dorsal extremities, and consequently 

 turned towards the endostyle instead of being directed to the 

 cloaca. The products of these organs are consequently thrown 

 into the dorsal portion of the atrium, far from the cloaca. 



There is only one reproductive mass in M. arenosa ; it is larger 

 than usual, is of irregular form, and belongs to the right side of 

 the mantle, but overlies to a considerable extent the alimentary 

 tube. The oviduct, as usual, opens into the cloaca ; but the vas 

 deferens has not yet" been observed, though the male secreting 

 organ is distinctly visible, forming a considerable part of the 

 mass. 



In Clavelina lepadiformis, one of the Social Ascidians, the geni- 

 talia are placed in the loop of the intestine, near to the lower 

 extremity of the abdomen, the ovary lying on the right of the 

 alimentary tube, the testis being spread over both sides of it. 

 The former resembles a bunch of grapes in which the berries are 

 of various sizes ; and the oviduct, like the stem of the fruit, is seen 

 in the midst of the ova ; and I believe I have traced it passing 

 up the abdomen in the direction of the cloaca, but did not suc- 

 ceed in determining its outlet. M. Milne-Edwards, in his well- 

 known work on the " Ascidies composees"t5 states that he could 



* "Recherches sur rEmbryogenie, I'Anatomie, et la Physiologic des Ascidies 

 Simples," M^moires de I'Academie Royale de Belgique, t. xx., 1847. 

 t ' Observations sur les Ascidieii composees des cotes de la Manche,' p. 22. 



