358 Mr. Robert Garner's Malacological Notes. 



must be imported into classification. Thus, in animals nearest 

 the boundaries of the vegetable kingdom, the special character 

 of life-force of the latter seems not extinct, causing a rayed 

 or ramose disposition and a tendency to budding in their mode 

 of increase ; or we may say that animal life presupposes the 

 vegetable, being itself but the manifestation of the same en- 

 dowment in a higher form — just as, according to some, psycho- 

 logical phenomena are superadded to, or developed from, the 

 physiological*. Again, amongst the disturbing influences 

 which affect whole series of animals, the nature of their loco- 

 motion must be reckoned ; for to an adaptation for this and for 

 aerial or aquatic life can probably be referred many aberra- 

 tions, such as metamorphosis or alternation of generations ; and 

 hence it is that a more regular ascent from the simple to the 

 complicated animal ought to be seen when we confine our- 

 selves to one form of life, say the aquatic. 



The same aberrations render it difficult to trace the phylo- 

 geny of an animal — that is, to show from what antecedent 

 form, extinct or existent, it originated, and through what 

 phases its species passed. We see enough in nature to recog- 

 nize, as already alluded to, one general plan of formation ; and 

 at the origin of all animals, or in the embryo stage, there is, as 

 the rule, much sameness — and first either a division or a bud- 

 ding of a pullulating plasm, or an origin from the union of a 

 simple cell and microzooid ; but remarkable differentiations and 

 variations occur early, almost withdrawn from our observation, 

 and their rattoncde not always understood. It is true that, 

 a more or less intimate segmentation of the yelk of the ovum 

 in all Invertebrata produces the morula form, preceding all 

 development ; but there is no complete uniformity further, and 

 the variations remain unsystematized. The morula or granu- 

 lated sphere may become hollow, and then be invaginated, so 

 as to form a sacciform gastrula^ so called ; and Haeckel con- 

 sidered this to be the animal stock-form ; but even in the cases 

 where it prevails the morula may be first changed into a flat 

 planula^ and the sacciform disposition be attained, somewhat 

 differently, by its flexure f. The cavity may also form in the 

 interior, without any flexure or invagination, or with the latter 

 imperfect ; and in the normal gastrula it does not follow that 

 the primary opening becomes the mouth, or the primary cavity 

 or hlastocele the permanent stomach ; and before any cavity 



* Mr. Spencer teaches that the processes of morphological differentia- 

 tion conform to the same general laws in the one kingdom as in the other 

 (' Biology,' vol. ii.). 



t Salenskv, " On Haeckel's Gastrtpn Theory," Ann. & Mag. Nat. Hist., 

 Jan. 1875. 



