10 



INTRODUCTORY LECTURE. 



Still closer becomes the link between the parent and offspring in 

 the Mammalian class, bj the substitution, for the exclusion of a pas- 

 sive irresponsive ovum, of the birth of a living young, making 

 instinctive irresistible appeal, as soon as born, to maternal sympathy ; 

 deriving nutriment immediately from the parent's body, and both 

 giving and receiving pleasure by that act. 



These beautiful foreshadowings of higher attributes are, however, 

 transitory in the brute creation, and the relations cease, as soon as 

 the young quadruped can provide for itself. Preservation of off- 

 spring has been superinduced on self-preservation, but there is as 

 yet no self-improvement : this is the peculiar attribute of mankind. 

 The human species is characterised by the prolonged dependence of 

 a slowly maturing offspi-ing on parental cares and affections, in which 

 are laid the foundations of the social system, and time given for in- 

 stilling those principles on which Man's best wisdom and truest hap- 

 piness are based, and by which he is prepared for another and a 

 higher sphere of existence. In this destination alone may we dis- 

 cern an adequate end and purpose in the great organic scheme deve- 

 loped upon our planet. 



In ascending to Man, we trace a very extensive and varied, but 

 progressive course of development, through the great Vertebrated 

 Sei'ies, which commences at a very low point. 



It might, perhaps, be imagined that the lowest Vertebrated form 

 began where the highest Invertebrated form ended, and made a direct 

 step in advance in the scale of Animal Organisation. Such, indeed, 

 ought necessarily to follow on the hypothesis of the development of 

 species by progressive transmutation, and of the arrangement of 

 animal life in a single and uninterrupted chain of being. 



But truer views of the nature and direction of Zoological affinities, 

 and a deeper insight into the laws of Development and of Unity of 

 Organisation in the Animal Kingdom, concur to disprove those once 

 favourite and recently-revived hypotheses. We have seen that the 

 Invertebrata resemble each other only at the earliest and most tran- 

 sitory periods of their development, diverging thence, in special 

 directions, to the manifestation of very distinct types of animal struc- 

 ture. So likewise we must look to the very beginning of the de- 

 velopment of the Vertebrate animal before we shall discover that 

 amount of concordance which will justify us in predicating "Unity 

 of Organisation" between it and any of the Invertebrated forms. 

 And when, with infinite cai'c and minutest scrutiny, availing our- 

 selves of all the aids and appliances of optical art, we have arrived 

 at clear and satisfactory demonstration of the greatest amount of re- 

 semblance, in constitution and properties, between the Vertebrate 



