66 METAMOKPHOSES OF MAN 



The changes which the organs of circulation and 

 respiration undergo are not by any means as well 

 known as those we have been describing, and this 

 ignorance is due, most likely, to the great simplicity 

 of the first, and the equally complex character of the 

 second. In this caterpillar, as in every other one, 

 the circulation is almost entirely lacunar. In it, as in 

 the butterfly, there is a distinct heart, or rather its 

 representation, in the form of a long many-chambered 

 canal, stretching from end to end of the body. When 

 the latter is shortened, this dorsal vessel, as it is called, 

 is also diminished in length, and becomes more and 

 more tortuous, in proportion as the regions of the 

 body are mapped out and separated from each other. 



This degradation of the circulatory organ is com- 

 pensated for by the formation and distribution of a 

 series of respiratory organs, or tracheal These open 

 externally at the stigmata to which we have alluded 

 already. They consist, in Pieris, as in all other cater- 

 to form a complete history of this butterfly. Those, however, who 

 desire to pursue the study of the nervous system in insects, should 

 consult the memoirs devoted to this subject by the English naturalist 

 Newport, who was prematurely called from the field of science. 

 His work upon the nervous system of the privet-moth (Sphinx 

 Ligustri) is characterized throughout by clear powers of observation, 

 accurate demonstration, and really scientific deductions. Daily, 

 nay hourly, he followed the modifications which the nervous sys- 

 tem undergoes, not only in the species on which his work is written, 

 but also in the case of the nettle-butterfly. He proved that even 

 in the course of a single hour the brain undergoes very appreciable 

 changes in both its form and the disposition of its optic nerves. — 

 (" On the Nervous System of the Sphinx Ligustri," Philosophical 

 Transactions, 1832.) The metamorphoses (general and special) of a 

 butterfly are also described in the splendid work of M. Cornalia 

 on the Silkworm, " Monografia del Bombice del Gelso." 



