LECTURES ON EMBRYOLOGY. 



51 



lata in general, and are seen in the lowest forms, as 

 well as in the Lobsters (Plate VI), or Scorpions 

 (Plate VIII), or any of -the insects. 



That this mode of growth is not peculiar to in- 

 sects alone, but is characteristic of Articulata at 

 large, follows, from the beautiful investigations of 

 the embryonic growth of Crustacea and Spiders, 

 which have been traced by many Naturalists, but 

 above all by Herold, Pvathke, Ercil, &c. 



That the same mode of growth is also observed 

 in Crustacea and Spiders, can be satisfactorily as- 

 certained by a glance at plate III, where in a 

 Shrimp the germ is seen developing below the 

 yolk. 



[PLATE ITI YOUNG SHRIMPS.] 



Tne details of tueae metamorphoses I s>hall illus- 

 trate thereafter. I mention it now, only in or- 

 der to add, that this mode of growth is not pecu 

 liar to insects alone, but that it is characteristic of 

 most Articulata to have this inverted mode of 

 growth from their earliest embryonic condition. 

 They grow, as it were, in opposition to all other 

 animals. And it is a fact in no small degree re- 

 markable, that among such animals there should 

 be such a number of Parasites. Articulata are, 

 however, the only type in the animal kingdom" in 



h.ch parasitism is the prevailing rule, though 

 there are other Parasites which belong to other 

 classes. 



The metamorphoses of Insects which take 

 place after the little Larva (as Entomologists call 

 the earlier condition of the animal) is born, have 

 been extensively studied. This* little Worm (Plate 

 VII, fig. F) is like the primitive form of the com- 

 mon Mosquito, of which we see (Plate IX, figs. B> 

 B, C) all the different changes which the animal 

 undergoes before it is changed into its perfect 

 state. Figs. D, E, F represent the same successive 

 changes from the Horsefly (CEstrus) ; figs. G, H, I, 

 those of the common Flea ; figs. J, K, L, M, those 

 of the Cochineal. In plate X, the figs. A, B. C 

 represent the egg, larva and perfect Hemerobius ; 

 figs. D, E. F the metamorphoses of a Moth, of the 

 genus Geometra ; figs. G, H, I those of Phryganea, 

 and figs. J, K. L those of an Ephemera; plate XI 

 represents Beetles; figs. A, B, C the metamorpho- 

 ses of a Dermestes, whose larva is hairy and col- 

 ored, like that of a Butterfly ; and figs. D, E, F, 

 that of a Cetonia, in which the larva is a Maggot. 

 The Naturalists of the last century have studied, 



more carefully and more extensively the metamor- 

 phoses of insects than the Entomologists of the 

 present day. It is to works long since almost for- 

 gotten among entomologists, that we must resort 

 to find extensive, minute, and correct information 

 upon the metamorphoses of Insects in their vari- 

 ous stages of growth, bwammerdam, in his Bible of 

 Nature, full of interesting details, has given a great 

 variety of metamorphoses. So have the investiga- 

 tions by Degeer, Geoffroy, and Rosel, done more 

 in this department than all modern investigatiors 

 put together. 



[PLATE IX METAMORPHOSES or THE MOSQUI- 

 TO, HORSEFLY, FLEA AND COCHINEAL. 



The title of Rosel's work, which he styles 

 "Amusements with Insects "(Instktfn Belustigunyen) 

 shows how much he must have enjoyed his re- 

 searches. He has, perhaps, illustrated the meta- 

 morphoses of insects more fully than they have 

 been examined before or since. In our modern 

 times, Entomologists have devoted almost all their 

 attention to the study of genera and species, of the 

 external forms of families and specific distinctions, 

 and have in this way, endowed Entomology with 

 treasures of detail, but have made very few refer- 

 ences to the study of metamorphoses, which would 

 however, render this minute knowledge of details 

 much more valuable; for if the changes which take 

 place in various families were brought under rules, 

 these details would at once be made useful in the 

 comparison of extensive series. But, for the pres- 

 ent, we have only to hope for a general comparison 

 between the modifications of parts as they occur 



