TO THE FIVE GREAT TYPES. 267 



of the subject, I will merely state some of the general results of 

 these investigations, as far as they have a direct bearing upon the 

 point which we are now discussing. Lereboullet discovered that 

 not only will an egg divide into two distinct individuals at the 

 outset, but also, in some cases, the two individuals are formed 

 so closely side by side that the right side of one and the left side 

 of the other become more or less united, and form, at the point 

 of junction, a single trunk. Sometimes this occurred at the tail, 

 sometimes at the middle, or at the head; and the manner in 

 which the united parts are joined to each other shows clearly 

 and unmistakably that the right side of an animal is not neces- 

 sarily a different part of the body from, and in direct opposition 

 to the left side ; for we see that the one may take the place of 

 the other ; and we might say without exaggeration that they are 

 mutually interchangeable. This could not possibly happen, if 

 the two halves were not positively identical with each other. In 

 this sense, then, the body consists of two individuals acting as 

 one ; it is a duality. 



From this point of view, then, I think we may see that there 

 is a certain form of connection between the ideal relations of 

 bipolarity, bilaterality, and the type of division, on the one hand, 

 and, on the other hand, the reproductive process, which is the 

 basis of relation by consanguinity. It is, then, through this pro- 

 cess, that, from the apparently purely ideal relations of all animals 

 to each other, the transition is made to those relations or ties of 

 consanguinity which bind certain groups, as it were, in one family. 

 We cannot say where the ideal relation meets or interlocks with 

 the relation by blood ; the point of junction seems to vary in 

 the different groups. Among the lower forms of animals the 

 ideal relations of bipolarity and bilaterality are the most prom- 

 inent, and the division type is but faintly shadowed forth ; but, 

 as we rise in the scale, the latter becomes more decided, and 

 sometimes so strongly presents itself as to nearly obscure bilat- 

 erality. This is most notable among Starfishes and Jelly-fishes ; 

 and it has misled some into the belief that radiation is the pre- 

 dominant feature to which all other characters are subordinate 

 in these animals. 



