Mr. Robert ( Janicr's Mulacoloyical Notes. 3C1 



due perhaps to the necessary arrangement of the inlets and 

 outlets of the body in sueh animals as are encased and pro- 

 tected by a sliell or in other ways. Mr. Spencer attributes 

 the jointed form in the great subkingdom Articulata to rejjeti- 

 tion or budding, yet of a less njeciianical origin than the jointed 

 but adaptive disposition of the Vertebrata. Notwithstanding 

 this low vegetative characteristic of the Articulata, if it hold 

 good, they and ^lollusea are commonly considered to form 

 two parallel zoological divisions, rather tiian one concatenated 

 series. Upon the whole, tiie M(jllusca approach nearer to the 

 Vertebrata, as will become evident hereafter ; but the Articu- 

 lata are highly developed for locomotion, which ensures per- 

 fect meclianical structure and symmetry; they are less gene- 

 rally a(]uatie, and often adapted for aerial movement, to 

 which last the Mollusca cannot fairly be said to attain ; they 

 also evince wonderful ])owcrs of what looks like observation 

 and purpose. At the same time the Mollusca present varied 

 means of locomotion and of domiciling themselves ; and their 

 intelligence may be greater than our means of observation 

 enable us to ascertain ; the locomotion, however, with the ex- 

 ception of that of the pelagic swimmers, is generally of a simple 

 kind, mere gliding or creeping i-ather than walking, the 

 organs being formed with greater reference to hydraulics than 

 mechanics. They are anchorites accommodated to their cells, 

 sensitive rather than locomotive unities, seldom having any 

 repetition of parts of an analogous kind, but commonly 

 possessing, as already observed, more or less of that lateral 

 duplicity present in all animals above the liadiata — though, 

 indeed, in the Gastropoda this is liable to be interfered with 

 by an atrophy of one side. Altogether a moUusk is a ty[)ical 

 reality, showing either an origin from some primary molluscan 

 root, or a uniformity of special plan throughout their own 

 subkingdom. As a rule there may be said to be seen in them, 

 as we have them at present, an ascent from their lowest to 

 their highest forms, without any great hiatus — in this, more 

 than in their geological sequence, agreeing with the theory 

 of the derivation of one kind from another. 



If we are to trace up the Mollusca to their origin, their 

 biological pedigree, we shall, it is commonly held, an-ive at 

 the Bryozoa, or rather, to our mind, at the lowest Ascidite. 

 It seems far-fetched to form an alliance, as Cuvierdid, between 

 the Teredo and the articulate Lcpas, though there is an obvi- 

 ous analogy between the valves and adductor muscles of the 

 last and those of a bivalve mollusk — one of those curious 

 resemblances often occurring in nature between animals far 

 removed from each other, evnicing, on the one hand, relation- 



