4-lG Prof. M'Intosh on the 



museular anterior region of the body, and the relaxation of 

 its retractor muscles, cause the proboscis to yield readily to 

 the powerful stream of blood that is sent against it from 

 behind, and it smoothly unrolls outward from the transverse 

 margin of the lower lip like a very supple membrane, the 

 pinkish colour of the blood shining through the translucent 

 tissue. The extrusion goes on until the brownish mass of 

 the pharyngeal region of the digestive canal approaches the 

 front of the first body-segment, and sends the muscular coil 

 into the base of the proboscis, and partly under the long 

 retractor on its way to the tip — like a plug, — assisting to 

 retain the blood therein and giving solidity to the whole 

 organ. Thus, in its progress forward, the flattened snout is 

 thrust amongst the sand with an undulating and insinuating 

 motion till it has advanced about its own length ; then the 

 proboscis is ejected to its full extent, like an indiarubber 

 dilator, so as to make a suitable channel for the occupation 

 of the body while again pressing onward the exploratory 

 snout. Then all the retractile arrangements are brought 

 into play — the fan-shaped veitical fibres pull in the basal 

 (anterior) region, the short and long retractors act on the 

 entire organ, and the withdrawal of the pharyngeal pro- 

 trusion makes an open channel for the backward stream of 

 blood, which rushes into the vessels of the anterior region 

 out of the returning organ, further constricted by its own 

 circular muscular coat. These alternate protrusions and 

 retractions are repeated at somewhat regular intervals, and 

 continued for a long time. Moreover, an explanation is 

 perhaps afforded of the fact that the animal is partial to fine 

 sand, seeing that the larger sharp fragments of coarse gravel 

 and sand might injure either snout or proboscis, though the 

 latter is specially protected by its chitinous investment. 



Puncture of the anterior region of the body, so as to 

 give exit to the blood, interferes with the extrusion of the 

 proboscis ; indeed, it is not generally thrust out after such 

 an injury. 



The exsertile pharyngeal region is followed by a mobile 

 part of the alimentary canal that undergoes considerable 

 elongation w^hen the former is thrust forward, but which is 

 variously coiled in retraction. In transverse section it is 

 firm, often somewhat quadrangular, and consists, from within 

 outward, of the chitinous-like inner tunic, the glandular 

 layer (of less depth than in front), the basement-tissue, and, 

 lastly, of an external coat of circular muscular fibres. After 

 a short course baclcAvard the calibre of the canal diminishes, 

 and a distinct sheath from the vascular svstem envelops it 



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