84. Elliot, hihcritance of Acquired Characters. IJaimary 



The germ-plasm, according to Weismann's theory, can pro- 

 duce body-plasm, but the latter can never originate germ-plasm. 

 Germ-plasm is continuous, vmdying, the body-plasm is mortal. 

 On this point Prof. Lloyd Morgan* remarks, "I cannot but regard 

 his doctrine of the continuity of germ-plasm as a distinctly retro- 

 grade step. His germ-plasm is an imknowable, invisible, hypo- 

 thetical entity. Material though it be, it is of no more practical 

 value than a mysterious germinal principle. By a little skilful 

 manipulation, it may be made to account for anything and every- 

 thing The fiction of two protoplasms, distinct and yet 



commingled, is, in my opinion, little calculated to advance our 

 knowledge and comprehension of organic processes. For my- 

 self I prefer to stand on protoplasmic unity and cellular con- 

 tinuity." 



Mr. Lucasj' has shown how the change of habit in certain birds 

 of the island of Guadalupe, due to their insulation, illustrates 

 certain facts affecting skeletal variation. The descendants of 

 migratory species having their habitat restricted, show the symp- 

 tom of weakening flight in the decrease in the lengtli of the 

 sternum ; later on a diminution in depth of keel takes place. 

 Then follows a reduction in length of wing, beginning with the 

 nianus and fore-arm, the humerus apparently not being affected, 

 until the rest of the wing is perceptibly lessened. Then the 

 outer wing bones disappear, leaving only the humerus, — as in 

 Hesperornis^ — and finally the humerus itself may be wanting, as 

 in Dinornis giganteiis . But there are exceptions to this, and 

 one is exhibited in Salpinctes guadahipensis which has gained 

 in power of flight, both the wing and sternum exceeding in length 

 those of the continental form, and this would seem to indicate 

 that insulation does not necessarily cause degeneration. Mr. 

 Bryant had shown that this Wren had become the most abundant 

 species on the island, and in ten years had exhibited a slight in- 

 crease in length of bill ; and Mr. Lucas argues that in this species 

 superior wing power would give superior ability to obtain food, 

 to escape its enemies, and to prevent its being blown out to sea, 

 and a superiority in these points would naturally lead to its in- 

 crease. Why this bird should be an exception to the others on 



*Anim. Life and Intell. p. 141, 

 fAuk, 1891, p. 2i8. 



