228 Transactions of the American Institute. 



organs i-ednced to two pairs; in the lowest class, the fishes, these are 

 represented by simple fins, and assist but little in locomotion, this 

 act bein<!; performed by the tail. In the reptiles le<^s first appear. 

 In the birds the fore lei^s are specialized and converted into wings. 

 Among the mammalia the lowest members again recall the fishes 

 in the reduction of the fore legs to fin like organs, and the head is- 

 enormously proloTiged beyond the brain, which occupies a small 

 cavity. Taking only the more prominent groups, we see in the her- 

 bivorous animals the legs used simply for locomotion, the head 

 degraded to purposes of self-defence, and generally armed with pi-omi- 

 iient horns. In the carnivorous animals the fore legs now aid in 

 securing their food as well as performing the act of locomotion. In 

 the monkeys the fore legs not only perform the act of locomotion, 

 but also convey food to the mouth, and hold the young to their breast 

 in nursing. In man, the highest vertebrate, the fore legs are removed 

 entirely from the locomotive series, and become subservient to the 

 head. It is interesting to review the relative attitude of the difierent 

 animals in their relation to the world ; thus the lowest radiates are 

 rooted to one spot, and in this respect represent a vegetative character ;. 

 in tlie other members of this branch they move head downward as in 

 the jelly fishes and star fishes. In the next branch, the mollusca, the 

 lowest members are buried head downward in the mud. In the snails 

 the head is generally below the bulk of their body. In the cuttle 

 fishes the head is on a level with their body, or in other words, the 

 antero-posterior axis is horizontal while swimming, but in crawling, 

 the head is below, and a mean line representing the antero-posterior 

 axis for the branch, would be on an angle of forty-five degrees, thfr 

 head downward. 



In the articulates the antero-posterior axis is horizontal. Of the ver- 

 tebrates, the fishesare horizontal, and in the reptiles the head becomes 

 slightly elevated, while in the birds and mammals the head is still more 

 elevated, so that a mean line representing the antero-posterior axis, 

 for all the vertebrates not including man, would be 

 at an angle of forty-five degrees, the head above. ,^^ 

 And in man, as we have just shown, this line is 

 verticle, the head uppermost. Thus the following • Moiiu"k»*' 



diagram would represent the relative position of the X \ uadiates. 

 antero-posterior axis for the various branches, the I 



knob at the end of the line indicating the head. 



The lecturer closed by quoting from Agassiz : " Man is the crown- 



Mnn. 



VtTtobrates. 

 iculuies. 



