CEPHALOPODA. 367 



thereby procreates in its immature, and, as it seems, virgin state, like 

 the wingless larvae of the summer Aphides ; they may enter the 

 unimpregnated oviducts of these insects, and be there developed in 

 the manner which has already been described.* 



Did time permit, I might easily multiply the instances from the 

 Invertebrate organisations, which bear directly on the establishment of 

 the most important general laws in physiology. I shall conclude by 

 adverting to one which is alike interesting to the anatomist and natu- 

 ralist, and which has exercised the powers of the most exalted intellects 

 of the present age. To the disquisitions and discussions in which 

 Goethe, Oken, Cuvier, and GeofFroy have taken part, the doctrines 

 of Morphology and Unity of Organisation owe their existence. 



Some of the medical acquaintances of John Hunter, who, we are 

 told, complacently apostrophised his pursuits, in the language of pity, 

 when they found him dissecting a snail, a bee, or a worm, little 

 dreamt of the expanded views of the animal organisation at which he 

 was obtaining glimpses through those narrow casements. It would 

 seem that Hunter himself was oppressed with the grandeur of the 

 prospect, with the extent of the generalisations which his investiga- 

 tions of the lower animals, and of the embryonic forms of the 

 higher ones, were forcing upon his reflective mind, if we may judge 

 from his struggles to express ideas, at that period so novel and so 

 vast, and to which he could but give imperfect utterance. " If we 

 were capable," he says, " of following the progress of increase of 

 the number of the parts of the most perfect animal, as they first 

 formed in succession, from the very first, to its state of full perfection, 

 we should probably be able to compare it with some one of the in- 

 complete animals themselves, of every order of animals in the 

 creation, being at no stage different from some of those inferior 

 orders ; or, in other words, if we were to take a series of animals 

 from the more imperfect to the perfect, we should probably find an 

 imperfect animal corresponding with some stage of the most per- 

 fect."! 



With the great accession of facts with which Comparative Anatomy 

 has since been enriched, particularly from monographs detailing dis- 

 sections of the Invertebrate animals, we may now attempt a more exact 

 enunciation of the resemblance which a higher organised animal pre- 

 sents to those of a lower order in its progress to maturity : and the 

 consequent extent to which the law of ' Unity of Organisation ' may 

 be justly, and without perversion of terms, be predicated of animal 

 structures. We shall see some grounds for the statement that the 



* Lecture XVITL Insecta, p. 235. 



•}• Hunterian MS. quoted in Physiological Catalogue, vol. i. p. 4. 



