UNITY OF SYSTEM. 



(either visible or invisible to his naked eye, wafted by the winds or air, 

 however unperceivable to the feelings of man) in quest of food — a wise 

 arrangement of the Great Almighty, who provideth for all, from the micro- 

 scopic insect to the biped who calls himself lord of the universe. If it were 

 not for the numerous insect enemies with which the Aphides are surrounded, 

 these prolific insects would multiply to such a degree, that they would 

 finish by totally drying up the plants, which as it is they disfigure so much. 



According to Swainson, our species of Aphides are not found in South 

 America, but their place is supplied by numerous species of Membrocis 

 Centrobus, Lat., which are in fact the plant-lice of that continent. 



The Aphides are in general so similar in appearance and structure, that 

 when we see one or two we may imagine to ourselves thousands as being 

 in every way like them. They are oblong, conical, oval, soft and pulpy 

 bodies; head furnished with a pair of long slender antennae, which are 

 reflected when in a state of repose, but in walking are directed forwards 

 alternately to either side. It has six long and slender legs; the mouth 

 consists of a thin tube, sometimes three- fourths of the length of its body, 

 and when not employed is folded under the breast; with this instrument 

 it pumps up the juices of the plants they infect. Wings, where they exist, 

 are large and thin, crossed by a few strong ribs. Body peaked at the 

 tip, and a little before it there are two short diverging tubes. In their 

 habits they are sluggish. Their colours are varied, some black, some green, 

 some yellowish, and some mottled, etc. Some covered by cottony fila- 

 ments, and some quite transparent. But amidst this sameness, which 

 tends to keep them united, there are several with strong individual char- 

 acteristics, which form so remarkable a feature in the works of nature, and 

 contribute so much to the pleasure we derive from their contemplation. 



In our next we will attempt to describe some of the most injurious of 

 these insects, and those who may require a more detailed account, I must 

 refer to the papers of Mr. Walker, in the "Ann. Mag. BT. Hist." 



December, 1856. (To be continued.) 



ON UNITY OF SYSTEM. 



(Continued from page 29.J 

 "Thro' ceaseless change to seek th' unchanging Pole," 



The colossal birds of other days, some of which were at least twice the 

 size of the Ostrich, are well known. They built no nests for their eggs, 

 had no care for their young, and were degraded in size and in number of 

 kinds before the epoch of the nest-building, musical, and bright-hued birds. 



The next especial degradation occurred with the age of Mammalia, or 



