358 Mr. Robert Garner's Malacological Notes. 



must be imported into clas.-=;ification. 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 disjiosition 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 develo])ed from, the 

 physiological*. Again, amongst the disturbing influences 

 which aftect 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 refeiTcd 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 variations occur early, almost withdrawn from our observation, 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 rationale 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 (/astrula, 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 Salensky, " On Haeckel's Gastra>a Theory," Ann. & Mag. Nat. Hist., 

 Jan. 1875. 



