LUMBRICUS. 



137 



covered by the sea, this creature is extremely impatient of light ; and in 

 confinement it continually attempts to penetrate downwards, even when 

 there is no sand in its vessel. But if amply provided with this material, 

 it soon screens itself from view, and in burrowing, the head, enlarged, 

 as shewn by fig. 2, seems to be employed in effecting its descent. 



These animals form a thin coating of sand, which is of some tenacity, 

 investing the body just like a piece of thin linen wrapped around it. 

 When a specimen is removed from its residence, it seems to attempt 

 divesting itself of this covering, and to experience difficulty in doing so. 



The distinctive character of the species consists in the branchiae, oc- 

 cupying only an intermediate portion of the body ; the posterior, there- 

 fore, bearing none, is of different formation. 



2. Another species of the Lumbricus marinus, which I have not 

 hitherto observed to be described, though it is unlikely to have been 

 overlooked, inhabits our seas. 



This is somewhat smaller than the former, the body consisting of 

 numerous setiferous and branchiferous annulations. 



The branchije commence, as in the other, at some distance from the 

 anterior extremity, but they continue, without interruption, down to the 

 posterior extremity, or its immediate vicinity, being about thirty-eight 

 pair in all. They occupy every segment from their commencement, 

 except the last. The lower extremity terminates in a knob. The 

 branchiaa are dichotomous, originating from a root, and successively sub- 

 dividing into several members. They are somewhat incurved, and some 

 of them have a faint reddish appearance towards the root, but of this 

 portion it is not easy to obtain a view. Their action much resembles 

 that of the branchiae of the Tercbclla. 



The setiferous papillae are prominent, running down from the ante- 

 rior to the extremity. There are about fifteen pair of pencils between 

 the anterior and the commencement of the branchiae. The pencils are 

 composed of several bristles. 



Colour of the whole animal very dark green. Plate XIX., fig. 4 ; 

 head when globular, fij. 5 ; branchiae, fig. 6 ; substances like ova, fig. 7. 



