DOTO. 



very readily fall off, and possibly may be detached, as Professor E. Forbes supposes, at the 

 will of the animal, but of this we have not been able to satisfy ourselves. Their deciduous 

 character has been thought by some to offer a decided objection to their being considered as 

 branchiae, and indeed the animal is quite capable of surviving the loss of the whole of these 

 processes ; but as it is now very well ascertained that the mollusca of this order respire also 

 by the skin, even in cases where the branchial organs are more decidedly speciallized, we 

 see no good reason for withholding the name of branchiae from these organs, though they may 

 perform that function less perfectly than the processes of some other genera of the order. 

 The foot is linear, and generally rather narrow. The anus is dorsal and lateral, forming a 

 small nipple on the right side between the first and second branchial processes. The aperture 

 of the generative organs is placed below the first branchial process on the right side. 



The anatomy of Doto, notwithstanding its general similarity to that of Eolis, differs 

 from it in some interesting particulars. 



The digestive system has the buccal mass much smaller than usual, of an oval form, 

 and unprovided with corneous jaws. The tongue is curved and placed in the mouth as in 

 Eolis ; it is stiff, slender, and exceedingly small, and is composed of upwards of a hundred 

 transverse plates each supporting a central tooth, directed backwards, and appearing, when 

 highly magnified, a little denticulated at the sides. From the small size and weak armature 

 of the mouth, compared with other genera, we think it likely that the animals of this genus 

 feed only on the soft parts of the corallines, on which they are generally found. The salivary 

 gland is ample. It lies above the generative organs on the left side of the body, and 

 extends forward to the buccal mass, opening by a slender duct immediately before it through 

 the inferior wall of the channel of the mouth. There is likewise another gland connected 

 with the channel of the mouth which is probably accessory to the above, though it differs 

 from it in structure. It is much smaller, and is composed of numerous minute oval sacs, 

 each furnished with a delicate and suddenly constricted duct: these sacs surround the 

 channel of the mouth, and pour the secretion into it on all sides just where it receives the 

 duct from the large salivary gland. With a high magnifying power they appear to be 

 covered over the inner surface with nucleated cells, having minute vessels passing from 

 them, which ramify over the inner surface of the sacs and unite as they descend towards 

 the ducts. The size of the vessels corresponds exactly with the diameter of the nucleus.* 



The oesophagus is long, very slender, and passes from the upper posterior dorsal aspect 

 of the buccal mass, increasing a little in size as it reaches the stomach, which is small 

 and elongated. The interior is minutely granulated, but does not appear to be raised into 

 folds or wrinkles. The intestine is very short and wide, especially at its junction with the 

 stomach, which takes place further forward than usual on the right side : the inner surface 

 is plicated longitudinally ; the plicae end abruptly as they reach the stomach. From this 

 peculiarity of structure, and the great width of the intestine, it seems probable that it may 

 have some other function to fulfil than that of conveying off the refuse of digestion. May it 

 not be in this canal that the nutritive portion of the food is absorbed into the digestive 



* We have been thus minute iu the description of this gland, as we think it likely to throw some 

 light on the ultimate structure of glands in general. We should suggest the probability that the 

 nucleus of the cell of glandular tissue may be nothing more than the orifice of a minute vessel, or 

 perhaps, in some cases, a mere opening through which the secretion passes. 



