378 Mr. Robert Garner's Malacological Notes. 



female glands appear without doubt to be combined in the 

 same individual (hermaphrodite) ; yet we suppose that, from 

 the antipathy of Nature to self-impregnation and from the 

 difterence of the period when the two glands mature and dis- 

 charge their secretions, the ova are commonly fertilized from 

 a foreign source, and that it takes place after they are dis- 

 charged, commonly in the pallial cavity. Such species are 

 perhaps atone time functionally male, at another female. The 

 embryo has sometimes means of transport, as the cercariform 

 larva of Tunicata or the ciliated young of Gastropoda, by 

 which it seeks a suitable habitat ; whilst the sedentary species, 

 on the contrary, are often fixed for safety by a byssus, formed 

 by an especial gland, the trace of which may be found, even in 

 the adult Aiwdon, between the surface of the foot and the 

 pedal ganglion, in the form of a brown, waxy, concentric, 

 globular body. In all the above and in Patella or Chiton 

 the essential glands of reproduction are very simple ; but in 

 other species, though still hermaphrodite or monoecious, as 

 Helix or Lymnceus^ they have many and very curious acces- 

 sories ; yet here the sexual union of two individuals is necessary, 

 or at least most common. 



The more locomotive bivalves, as Cardium edule^ or the 

 sea-mussel, have sexes distinct (dioecious), also a great number 

 of Gastropods and Cephalopods ; and union of these takes place 

 either immediately or, in some Cephalopods, as is now well 

 known, by means of a hectocotyhis. There has been question 

 respecting the little gland situated at the ending, or rather 

 beginning, of the double set of organs of the monoecious Pul- 

 monifera {Helix and Lymnceus)^ whether it is an ovary or 

 testis, or the two combined, and whether the corresponding 

 extremity of the shorter set of the duplicate organs is an ovary 

 or simply an albuminiparous organ*. The first gland, im- 

 bedded in the liver at the end of the spire, was considered to 

 be the ovaiy by Cuvier ; biit, according to Meckel, it includes 

 both ovary and testis, with distinct though combined oviduct 

 and vas deferens ; and of this opinion we have now no doubt. 

 The fact may be easily verified by pressing the gland and duct 

 between two glasses, and submitting the object to the lens ; 

 and, from the movement of the spermatozoa, it is a truly won- 

 derful object. In Onchidium this gland visibly consists of 

 two others, quite disjoined ; and in all moUusks it is connected 

 with the external male organ, but never, we think, without 

 first communicating with the semitransparent organ, now sup- 



* The substance of which it is composed, however, is not coagulable 

 by heat, but swells up and is very viscid in water. Bichloride of mercuiy 

 and alcohol coagulate it. 



