65 8 Organic Physics. [ A ugust, 



brain, face, and so on, appear, until every organ is duplicated. In 

 more extreme cases we have duplication of the lower limbs, a 

 double head, the head and part of the trunk double, and finally 

 the whole body double, the two halves being united either inti- 

 mately or by only a slight bond, like that of the Siamese twins. In 

 some cases a triple body has appeared. These twin formations are 

 not the result of a chance union of developing germs, for a com- 

 plete series of duplications, from the slightest to the most ex- 

 treme, are upon record. 



Another set of anomalies, that of cleft or division between the 

 lateral halves of the body, may perhaps be included in the same 

 class. An ordinary case of this kind is that of cleft or hare lip, 

 but it is found in every part of the dividing line of the body. 

 The two sexual halves seem to have a tendency to develop sepa- 

 rately, and this is perhaps a step in the process of duplica- 



The third class of anomalies alluded to is that of displacement 

 of organs. This also is of frequent occurrence. A few instances 

 will suffice for illustration. The twin internal organs, the two 

 kidneys, for instance, sometimes occur on the same side of the 

 body. Of the exterior organs, a case is on record in which the 

 thumb was missing on one hand, while a double thumb appeared 

 on the other. A more striking case is one in which one foot had 

 but a single toe, while the other foot had eight, one of these be- 

 ing partly cleft in indication of the ninth. Another case is that 

 of eleven ribs on one side and thirteen on the other. 



These anomalous births may have far more importance than 

 has been ascribed to them; possibly, indeed, they may be of 

 essential significance in the question of the origin of species. 

 But before considering their consequences, it may be well to con- 

 sider their cause. In doing so it becomes necessary to carry the 

 theory of the struggle for existence further back than is usually 

 done. Ordinarily it is made to apply only to the case of survival 

 of the fittest in mature forms or in well developed embryos. But 

 it may be applied with equal justice to the struggle for existence 

 between germs, or between the leucocytes of the blood. These 

 self-feeding amoeboid corpuscles battle for nutriment. It is not 

 probable that they all become fully generalised. Those most ^ 

 fully generalized possess the best nutrient relations to the blood, 

 and are most apt to survive. Those only partly generalized are 



