March 1891.] 



PSYCHE. 



39 



stages that, as has been described above, 

 the primitive larval Thysanuriform stage 

 is skipped or omitted from the develop- 

 ment. 



In Coleoptera and in the highly spe- 

 cialized orders of insects (XI to XVI) 

 a novel and disturbing influence appears, 

 due to the extraordinary importance of 

 the functions of larval life. This period 

 in the larger number of groups in other 

 classes of animals is much less variable 

 than the adult stage, and it is really very 

 often a mere vehicle for the record and 

 transmission of hereditary characters. 

 In some of the orders of insects, how- 

 ever, it is as efficient for the manifesta- 

 tion of new modifications and adaptive 

 characters as the adult, and often per- 

 haps more variable. This is an excep- 

 tional rather than the usual aspect of 

 the larval stages, and makes the study 

 of insects remarkably difficult and inter- 

 esting. 



Sometimes in the orders I to IX (Coc- 

 cidae, Cicada), as well as more gener- 

 ally in X to XVI, the larvae carry the 

 line of development and modification a 

 long way outside of what can be termed 

 the normal or direct course, but these 

 deviations lead, as a rule, back again 

 through similar pupae to the same goal 

 in the imago, a typical adult insect. 

 Epicauta, the blister-beetle, is a good 

 example. Fig. 98 shows the active Thy- 

 sanuriform larva, and Figs. 102, 106, 

 107, the grub-like larva which passes 

 through two stages before becom- 

 ing the true pupa that transforms 

 into the imago. These complica- 

 tions were probably due originally in 



each type to the plastic nature of the 

 organism, which enabled it to fit itself 

 to different conditions and surroundings 

 during its passage through the younger 

 stages of growth. The history of para- 

 sites, whose loss of parts and correlative 

 modifications are plainly adaptations to 

 the nature of the surroundings in all 

 branches of the animal kingdom, shows 

 this to be sound reasoning. Among some 

 of these types there are all kinds of meta- 

 morphoses ami very complicated modes 

 of development, so that it is not difficult 

 to surpass even those of insects. One 

 can apply a similar nomenclature and 

 the same laws in explanation of the 

 often curious and sometimes extraordi- 

 nary metamorphoses, and these changes 

 are often, as in Taenia, accompanied 

 by corresponding acceleration and loss 

 of primitive stages. The curious trans- 

 formations of Echinodermata are plainly 

 adaptations of the larvae to a free life 

 in the water before they become attached 

 or sink to the bottom and begin their 

 proper life as crawlers. In this class 

 there are a number of examples of accel- 

 eration (Comatula, Spatangoids, etc.). 

 Such life-histories and those of Epi- 

 cauta, Sitaris and Meloe among beetles 

 which run out the gamut of changes 

 from the simplest Thysanuriform larva 

 through several grub stages to the qui- 

 escent pupa, show that the most 

 complicated metamorphoses, called hy- 

 permetamorphoses by entomologists, 

 must have arisen in response to the 

 changes of the surroundings. No other 

 hypothesis can account for the number, 

 variety, and novelty of these metamor- 



