518 GASTEROPODA. 



in the articulated Brachiopods should prove to be the same as the den- 

 dritic organ in the former, then in them also the sexes are combined. 



(1361.) Professor Owen supposed that the ova, when mature, escape 

 by the dehiscence of the pallial membranes. So long as no passage was 

 discovered leading externally from the perivisceral chamber, this could 

 be the only possible conclusion, but can now be no longer maintained, 

 for it has been ascertained that more than one such passage exists. The 

 natural inference would therefore seem to be that the eggs will find their 

 way through these passages, which may consequently be looked upon as 

 oviducts. 



(1362.) These curious organs were originally described by Cuvier as 

 hearts, in his well-known memoir on Lingula anatina, and subsequently 

 by Professor Owen on the Brachiopoda generally ; they open, however, 

 externally, and therefore can have nothing to do with the vascular 



(1363.) In Lingula the oviducts are rather peculiar in form, though 

 essentially the same as in the articulated Brachiopods. They are two 

 in number, and lie to a great extent between the two layers of the ilio- 

 parietal bands, stretching along the lateral walls of the perivisceral 

 chamber from the front to behind the dorsal attachment of the adjuster 

 muscles, and are so concealed by the viscera and muscles that very little 

 of them can be seen until these parts are removed. The expanded por- 

 tions open upwards and towards the lateral walls of the body, through 

 the processes of the ilio-parietal bands, close to the side-walls of the 

 chamber. They are of a yellowish colour, and terminate at the external 

 surface in two small diagonal slits, one a short way on either side from 

 the median line, a little below the mouth. The walls have a glandular 

 appearance, the inside being velvety from the numerous minute villi 

 which crowd the surface. 



(1364.) From the nature of these organs, it seems probable that the 

 ova on their passage outwards may receive some external covering. 

 In two instances in which the ova were mature, Mr. Hancock found 

 them in vast numbers strewed about the perivisceral chamber, and in 

 one of the oviducts several had penetrated nearly to the external orifice. 



CHAPTER XXII. 



GASTEROPODA* (Cuvier). 



(1365.) EXTENSIVELY distributed over the surface of the land, or in- 

 habiting the waters either fresh or salt, there exist a very numerous 



* yaarijp, the belly ; Troyp, a foot. 



