I.\\\ 01 V CE1 EH \ l [ON. -17 



in development, the author, in a previous paper,' Imagined 

 i often afforded i>> the young in Buch types to be 

 the efficiei B • the M raupialia are not the most highly sp.-,; 



mammals, nor are some of the penguins the most specialized birds, and yel both 

 :l the young in pouches. 1 > i ~t « .n i;i and mans other parasites arc ' 



ted, and yel in these we find exceedingly long and < plicated adaptive 



of metamorphoses, with a high degree of protection in son nd in 



kted i les of development with less protection, as in Taenia. 



r in bis •' Comparative Embryology " subsequently adopted the same ex- 

 planation in order to account for cases of " abbreviated development, 

 which In- noted, bul without, however, recognizing them as due t«» any genera] 

 r tendency of development, or making quotations of Cope's, Packai t 



the author's researches in this direction. 



'I'll. I» and other insects, whose larva' are placed in protected situations 



where ad, and bave consequently lost their useless jaws, eyes, legs, 



ami hard chitino ig, ami in • a the different 



• :' their ancestral forms, me very remarkable example- of acceleration in 

 ipment. I 1 the supply ami kinds of food, ami perhaps prob 



may have had much to do with these changes, as pointed out by several 



The constant correlation of habits ami structure in larvae is. however, 



independent >>!' protection; and it i- evident that such a limited cause could not 



produced, f, the universal tendency of acceleration. The hyper- 



- and parasites also shows thai protected ba 



- for protection, are not essential to acceleration, since 



the most complicated and indirect modes of development occur as in Sitaris, 



protected durii jes and unprotected at others. 



•ion occurs whether an animal is protected or unprotected, whether 



died with one Kind <>f food or another, in all sorts of habitats, ami whether 



This can he supported by 



: ■ animal-, described by other author- than those 



_ the truth of this law. 



With regard to Cephalopoda, thej arc 



usuall . -mailer, narrower, or lest 



■ h compressed, a- in I ( and in Oxynoticeras, 



when compared with their immediate progenitors. The more cylindrical whorls 

 Ophidioci and the compressed cylindrical fo I 



All of these more com- 

 ■ 1 or more rylindri were obviously not adapted t" the ofl 



in b very positive manner that 



within their whorls, and consequently less protection for 



the j n in the i neric normal forms. It is 



• I for the young ii 

 shells, S. ~ hich did not n in the 



lh compli r development from which th< 



