1904.] PACKARD — OPISTHENOGENESIS. 289 



tive in the Tyndale version in only 44 per cent, of all cases, while 

 which has risen from 16 per cent, in Wiclif to 50 per cent, in 

 Tyndale. Which was confined largely to nouns and that to pro- 

 nouns. In the eighteenth century, which declines in use in the 

 classical English of Addison and Steele, while that gains slightly in 

 frequency. A more marked change is manifest in the nineteenth 

 century in the English of Macaulay, where which refers to a noun 

 in 99 per cent, of all cases of its use as a relative, constituting a 

 marked feature of his style. In Matthew Arnold, this proportion 

 is preserved ; also, though in a less degree, in the writings of Mrs. 

 Humphry Ward. The present tendency is to subordinate the use 

 oithat, perhaps in part due to its use as a declarative conjunction, 

 while who has gained in frequency of use and refers mainly to per- 

 sonal nouns. 



Cornell University, Ithaca, April g, igo4. 



OPISTHENOGENESIS, OR THE DEVELOPMENT OF 



SEGMENTS, MEDIAN TUBERCLES AND 



MARKINGS A TERGO. 



BY ALPHEUS S. PACKARD, LL.D. 

 (Received June 15, 1904.) 



Weismann, in his suggestive Studies in the Theory of Descent 

 (1876), was the first to discuss the origin of the markings of cater- 

 pillars, and to show that in Deilephila hippophacs the ring-like spots 

 of the larva "first originated on the segment bearing the caudal 

 horn, and were then gradually transferred as secondary spots to the 

 preceding segments " (Vol. i, p. 277). 



Afterwards (i 881-1890), Eimer^ showed that in the European 

 wall-lizard " a series of markings pass in succession over the body 

 from behind forwards, just as one wave follows another, and the 

 anterior ones vanish while new ones appear behind." He speaks 



1 " Untersuchungen ueber das Variiren der Mauereidechse," Archiv /. 

 Naturg., 1881 ; " Ueber die Zeichnung der Thiere," Zool. Anzeiger, 1882, 1883, 

 1884; Organic Evolution, London, 1890. 



PROC. AMER. PHILOS. SOC. XLIII. 177. S. PRINTED SEPT. 29, 1904. 



