634 ADDITION'S. 



Dicotyledons is observed in germination, when the Dicotyledonous 

 radicle elongates and forms the root of the young plant ; the Mono- 

 cotyledonous radicle does not elongate, but pushes out rootlets from 

 itself at once. Hence the not vuy good terms, exorhizal for Dicoty- 

 ledonous, and endorhizal for Monocotyledonous. 



" The highest physiological generalization in the vegetable kingdom 

 is between Phanogama and Cryptogama. In the former, fertilization 

 is effected by a pollen-tube touching the nucleus of an ovule; in 

 Cryptogams, the same process is effected by the contact of a sperm- 

 , cell, usually ciliated (anther ozoid], upon another kind of cell called 

 a germ-cell. In Phsenogams, further, the organs of fructification are 

 all modified leaves; those of Cryptogams are not homologous." 

 (J. D. H.) 



ZOOLOGY. 



I have exemplified the considerations which govern zoological classi- 

 fication by quoting the reflexions which Cuvier gives us, as having led 

 him to his own classification of Fishes. Since the varieties of Qua- 

 drupeds, or Mammals (omitting whales, &c.), are more familiar to the 

 common reader than those of Fishes, I may notice some of the steps 

 in their classification ; the more so as some curious questions have 

 recently arisen thereupon. 



Linnffius first divides Mammals into two groups, as they have Claws, 

 or Hoofs (imguiculata, ungulata?) But he then again divides them 

 into six orders (omitting whales, &c.), according to their number of 

 incisor, laniary, and molar teeth ; namely : 

 Primates. (Man, Monkey, &c.) 

 Bruta. (Rhinoceros, Elephant, &c.) 

 Fera. (Dog, Cat, Bear, Mole, &c.) 

 Glires. (Mouse, Squirrel, Hare, &c.) 

 Pecora. (Camel, Giraffe, Stag, Goat, Sheep, Ox, &c.) 

 Belluce. (Horse, Hippopotamus, Tapir, Sow, &c.) 

 In the place of these, Cuvier, as I have stated in the Philosophy 

 (On the Language of Sciences, Aphorism xvi.), introduced the follow- 

 ing orders : Bimanes, Quadrumanes, Carnassiers, Rongeurs, Edentcs, 

 Pachyderms, Ruminans. Of these, the Carnassiers correspond to the 

 Ferae of Linnaeus ; the Rongeurs to his Glires ; the Edentes are a 

 new order, taking the Sloths, Ant-eaters, &c., from the Bruta of Lin 

 nseus, the Megatherium from extinct animals, and the Ornithorhynchus, 

 &c., from the new animals of Australia ; the Ruminans agree with the 



