128 HYPOTHESIS OF THE DEVELOPMENT OF 



being wanted, they are not developed, and baleen is brought 

 forward instead. 



But the most remarkable circumstance attending the law of 

 unity of organization is, that an organ is sometimes developed 

 to a certain extent, but wholly without use. 1 This organ will, 

 perhaps, be seen serving a purpose in a particular family of 

 animals ; but we advance into an adjoining or kindred family, 

 and there find a rudiment of the same organ, which, owing to 

 the different conditions of this new set of creatures, is of no 

 kind of service. Thus, some of the serpent tribes possess 

 rudimentary and totally useless limbs. In other instances, a 

 portion of organization necessary in one sex is also presented 

 in the other, where it is not necessary. For example, the 

 mammas of the human female, by whom these organs are 

 obviously required, also exist in the male, who has no occasion 

 for them. It might be supposed that in this case there was a 

 regard to uniformity for mere appearance' sake ; but that no 

 such principle is concerned, appears from a much more re- 

 markable instance connected with the marsupial animals. The 

 female of that tribe has a process of bone advancing from the 

 pubes for the support of her pouch, and this also appears in 

 the male marsupial, which has no pouch, and requires none. 



The same law of unity may be recognised in the vegetable 

 kingdom. Amongst phanerogamous plants, a certain number 

 of organs are always present, either in a developed or rudi- 

 mentary state ; and those which are rudimentary can often be 

 developed by cultivation. Flowers which bear stamens on one 

 stalk, and pistils on another, can be caused to produce both, or 

 to become perfect flowers, by having a sufficiency of nourish- 

 ment supplied to them. So, also, where a special function is 

 required for particular circumstances, nature provides for it, 

 not by a new organ, but by a modification of a common one. 

 Thus, for instance, some plants destined to live in arid situa- 

 tions, require to have a store of water which they may slowly 

 absorb. The need is arranged for by a cup-like expansion 



1 " I think it would be more correct to say, ' without apparent use.* 

 A very strong case has been made out by Mr. Paget, in his Hunterian 

 Lectures at the College of Surgeons, in favour of the rudimental de- 

 velopment of organs being necessary to withdraw from the blood some 

 element of nutrition, which, if retained in it, would be positively inju- 

 rious, like a retained excretion. (See Carpenter's Human Physiology, 

 p. 195.) This does not in the least interfere with the author's argu- 

 ment, but is, in fact, only a confirmation of it, carrying back the unity 

 to the formative fluid." MS. Notes of a Physiologist. 



