360 ^It. Robert Garner's Malacohyical Notes. 



at the early stages of life ; and with so many embryological 

 irregularities, or what at present seem such, what can we do 

 as regards classification but avail ourselves of plain morpho- 

 logical data ? With others of the advanced school M. Giard 

 is somewhat severe on the homologists, yet he dwells on the 

 very strong action of the exterior, as, for instance, in " the 

 convergence of types by pelagic life " *. 



In the following paper the Bryozoa or ciliated poly|ies are, 

 with some resei-\'e, included with the mollusks, nor is much 

 said respecting the lowest class of ti'ue mollusks, the Ascidia^ ; 

 it is the less needful, therefore, to dwell, as a prelude, on the 

 manifestation of the composite, branched and i-ayed vegeta- 

 tive tendency in these two classes, trenching upon the confines 

 of the molluscous subkingdom. In the latter (in Salpa, for 

 instance), though, for us, mollusks, we have remnants of all 

 these tendencies, as well as of alternation of generations — ten- 

 dencies all predominant in still lower animals, as, for instance, 

 in the plant-like infusorial Vorticella, or in the more minute 

 but proliferous and branched Dinohryon — almost equally com- 

 mon in our pools, but less easy to detect or examine, as it 

 swims freely about, mimicking the oceanic creature last 

 named, the Saljju ; in fact, it may be observed, en jjossant, 

 that the Infusoria, so called, in a broad sense^ stand alone 

 within the animal cosmos. Their minute size, depending 

 perhaps on a unicellular origin, and answering to that of 

 the Desmids in the vegetable kingdom, constitutes almost a 

 primar}' characteristic ; and they present faint resemblances to 

 other animals of several orders : they have the vibratile organs, 

 or cilia, so common in mollusks, capable of effecting locomo- 

 tion through the water in their own minute bodies, but bringing 

 the water to the animal for respiration and for the conveyance 

 of nutrient particles in the mature mollusk ; some also (the 

 Foraminifera) form shelly coverings, which simulate those of 

 the same animals. 



Animals have been arrangedf into those which are centrally 

 and those axially developed — that is, either in a radiate or a 

 longitudinal fashion : with the former the Mollusca, as already 

 intimated, cannot be well made to agree ; with the latter they 

 correspond no better. They have little of the axial arrange- 

 ment of an annelid, and not always, though generally, bila- 

 teral symmetry, confining ourselves to the animal in contra- 

 distinction to the vitaljorgans. Upon the whole, flexure super 

 5€, rather than any other plan, predominates, and prevails up- 

 wards in a great degree from the biyozoon to the cuttlefish, 



• ' Revue des Sciences Naturelles,' March 1875. 

 + ' Principles of Biology/ Spencer, vol. ii. 



