346 LECTURE XXIV. 



cavity which widens as it descends, and contains a soft caruncle, rising 

 from the bottom of the cavity like the piston of a syringe. When the 

 sucker is applied to any surface for the purpose of adhesion^, the piston, 

 which previously filled the cavity, is retracted, and a vacuum produced. 



The complex irritable mechanism of all these suckers is under 

 the most complete control of the predatory Cephalopod. My friend 

 Mr, Broderip informs me, that he has attempted, with a hand-net 

 to catch an Octopus that was floating within sight with its long and 

 flexible arms entwined round a fish which it was tearing to pieces 

 with its sharp hawk's bill ; the Cephalopod allowed the net to approach 

 within a short distance of it, before it relinquished its prey, when in 

 an instant it relaxed its thousand suckers, exploded its inky ammu- 

 nition, and rapidly retreated under cover of the cloud which it had 

 occasioned, by rapid and vigorous strokes of its circular web. 



The Cephalopods which frequent the more open seas, and which 

 have to contend with more agile and powerful fishes, have still more 

 complicated organs of prehension. In the Calamary the base of the 

 piston is enclosed in a horny hoop with a dentated margin. In the 

 Onychoteuthis the margin is produced into a long, curved, sharp- 

 pointed claw. These formidable weapons are sometimes clustered at 

 the expanded terminations of the tentacles, and in a few species are 

 arranged in a double alternate series along the whole internal surface 

 of the eight ordinary arms, as they were in the extinct Belemnite. 



In connection with the uncinated acetabula at the extremities of the 

 long tentacula of this Onychoteuthis *, you may observe also a cluster 

 of small simple unarmed suckers at the base of the expanded part. 

 When these parts in each tentacle are applied to one another, they be- 

 come locked together, and the united strength of both the peduncles is 

 thereby more effectually brought to bear upon any resisting object 

 which may have been grappled by the terminal hooks. This is a very 

 striking mechanical contrivance : human art has remotely imitated it 

 in the fabrication of the obstetrical forceps in which either blade can 

 be used separately, or by the interlocking of a temporary joint be 

 made to act in combination. 



In the diminished number, increased size and progressive complica- 

 tion of the cephalic muscular appendages, and in their final modifica- 

 tion for combining with one another to produce a determinate action, 

 we trace the common order which regulates'the development of other 

 parts of the animal organisation. In our past review of the Inverte- 

 brata, we have witnessed this order in the appearance of the more 

 essential organs, as the stomach, the heart, the gills, the generative 



* Prep. No. 166, D. 



