142 



SCIENCE. 



[N. S. Vol. XIX. No. 473. 



claimed, for it an important lunetion in 

 the regenerative process. Morgan, and 

 later Stevens, vs^orking upon the same hy- 

 droid, became convinced that the claims 

 of the former investigators as to the im- 

 portance of this pigment were not vpell 

 founded. They found that not only was 

 the pigment of no special importance, but 

 that it was really a waste product, and 

 that during the process of regeneration 

 was actually excreted and finally ejected 

 bodily from the hydranth. I have person- 

 ally been able to confirm these results on 

 the same and related hydroids, and have 

 also shown that in regenerating medusa 

 there is formed de novo in each regener- 

 ating organ, such as manubrium, radial 

 canals, etc., the characteristic pigment of 

 the normal organ. This was particularly 

 noticeable in the ease of radial canals. Fol- 

 lowing their regeneration and promptly 

 upon their functional activity the deposi- 

 tion of pigment made its appearance, and 

 within a comparatively short time had ac- 

 quired the normal intensity. This was also 

 true of other organs, tentacles and ten- 

 tacular bulbs, as well as manubrium and 

 canals. 



Substantially the same results have been 

 obtained, though here first announced, in 

 experiments upon one of the Seyphome- 

 dusiB. In very young specimens where the 

 tissues are delicate it is possible to note 

 the intense activity in regenerating organs, 

 such as the sensory body. The first part of 

 this organ to make its appearance is the 

 sensory papilla, which is soon followed by 

 the otoliths, and later by the special pig- 

 mentation of the entire organ. 



From the foregoing considerations three 

 things seem to me to be more or less evi- 

 dent: 



1. That in all regenerative processes a 

 very marked degree of metabolism is in- 

 volved, whether in the mere metamorphosis 



of old . tissues, into new, or in the direct 

 regeneration of new tissues by growth 

 processes, both of which seem to occur. 



2. That in regenerative processes there 

 is often associated the development of pig- 

 mentary substances which seem to have no 

 direct function in relation thereto. 



3. That in many eases there follows a 

 more or less active excretion and elimina- 

 tion of portions of the pigment in ques- 

 tion. 



Concerning color phenomena among the 

 several classes of worms we are in much 

 the same uncertain state of mind as in the 

 former. For while in some of the annelids 

 there may be found fairly well developed 

 visual organs it may be seriously ques- 

 tioned whether they are of any such degree 

 of perfection as would enable their pos- 

 sessors to distinguish small color distinc- 

 tions. And if this be the case there would 

 at once be eliminated any possibility of 

 conscious adaptation in seeking a suitable 

 environment, or such as would be involved 

 in so-called sexual selection. 



Furthermore, it is very well known that 

 among this group some which exhibit among 

 the richest of these color phenomena have 

 their habitat in seclusion, buried in sand or 

 mud, or hidden beneath stones, or with 

 tubes built up from their own secretions, 

 or othenvise so environed as to render 

 practically nil the operation of natural se- 

 lection. 



Again, it should not be overlooked in 

 this connection that in many of the anne- 

 lids, as well as others, the most pronounced 

 source of color is to be found in the hsemo- 

 globin dissolved in the blood, and that it 

 would be as futile to ascribe its color to 

 natural selection as it would to claim a 

 similar explanation of the color of the 

 same substance in the blood of vertebrates, 

 where, as color, it is absolutely of no select- 

 ive value, except in such special cases as 

 the colors of the cock's comb, where it may 



