EMBRYOGENY 209 



embryogeny which strives from the beginning towards 

 this peculiarity ? Why are the eyes, as with normal 

 fishes, always singly placed on both sides and travel 

 first of all in the young fish so as to come together ? 



We have thus learned of some cases in which the 

 individual evolutional history really explains to us 

 how the adult forms formerly appeared. 



It is scarcely necessary for us to emphasize the 

 fact that as regards the origin of those types themselves, 

 fish or crab types, we learn nothing at all, but only 

 how some fish and crabs can arrive at a form deviating 

 from the normal. It may, however, be emphasized 

 that everyone who accepts the above conclusion must 

 simultaneously agree that to each type there belongs 

 also a particular process of evolution, otherwise there 

 could not be expected, from the embryogeny, any 

 explanation of the systematic classification. 



(b) Of somewhat wider application are the conse- 

 quences of the conclusions which have been drawn from 

 observation of other dissimilar peculiarities of the 

 embryogeny of many recent animals. The Salamander 

 (Salamandra maculosa) is viviparous and produces its 

 larvse in the water. The larvae possess in conformity 

 therewith gills for breathing water and a rudder 

 tail for swimming. A quite near relative, the black 

 Alpine Salamander (S. atra), also viviparous, bears 

 only two to three young, which are born on land ; the 

 young are conformably provided with lungs for breathing 

 air and with a round tail for creeping. But these 

 young ones pass through, in the mother's body, a 



