MERISTIC PHENOMENA 49 



amples such a condition is shown to be a dominant we cannot 

 avoid the inference that some concrete factor has the power of 

 suppressing or inhibiting this division. Figs. 3 and 4 illus- 

 trate degrees of union between digits in the human hand and 

 foot. 



It is not in question that various other forms of irregular 

 webbing and coalescence of digits exist, and respecting the genetic 

 behaviour of these practically nothing is as yet known, Such 

 a case is described by Walker, 14 in which the first and second 

 metacarpals of both feet were fused in mother and daughter, 

 and several more are found in literature. Contrasted with these 

 phenomena we have the curious fact that in the Pigeon, Staples- 

 Browne found webbing of the toes a recessive character. The 

 question thus arises whether this webbing is of the same nature 

 as that shown to be a dominant in Man, and indeed whether the 

 phenomenon in pigeons is really meristic at all. There is some 

 difference perceptible between the two conditions; for in Man 

 there is not so much a development of a special web-like skin 

 uniting the digits as a want of proper division between the digits 

 themselves, and in extreme cases two digits may be represented 

 by a single one. In the Pigeon I am not aware that a real 

 union of this kind has ever been observed, and though the web-like 

 skin may extend the whole length of the digits and be so narrow 

 as to prevent the spread of the toes, it may, I think, be main- 

 tained that the unity of the digits is unimpaired. For the 

 present the nature of this variation in the pigeon's feet must be 

 regarded as doubtful, and we should note that if it is actually 

 an example of a more perfect division being dominant to a less 

 perfect division, the case is a marked exception to the general 

 rule that non-division is dominant to division. 



Reference must also be made to the phenomenon of fasciation 

 in the stems of plants. As Mendel showed in the case of Pisum 

 this condition is often a recessive. The appearances suggest 

 that the difference between a normal and a fasciated plant 

 consists in the inability of the fasciated plant to separate its 

 lateral branches. The nature of the condition is however very 



14 Walker, G., Johns Hopkins Hospital Bulletin, XII, 1901, p. 129. 

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