380 NOTES. 
intestinal Worms are, by some eminent naturalists, separated under the dis- 
tinct name of Helminthozoa. 
163 Apparent exceptions: Some lower forms have no branchie, but respire 
by the skin, usually of the legs, but this is substantially a gill; certain Crabs, 
also, live on dry land, but they manage to keep their gills wet. 
164 The student should remember that this threefold division is not equiy- 
alent to the like division of a vertebrate body. 
165 Each ring (called somite) is divisible into two arcs, a dorsal and ventral, 
and each are consists of four pieces. 
166 Sight and hearing are the only senses discovered in this class. 
167 The four pairs of legs in Arachnids answer to the two pairs of maxille, 
the great claws, and the first pair of legs of the Lobster. 
168 Compare the single thread of the Silk-worm and other caterpillars. 
169 The common Spider, Zpeira, which constructs with almost geometric- 
al precision its net of spirals and radiating threads, will finish one in forty 
minutes, and just as regularly if confined in a perfectly dark place. 
170 These parts do not correspond to the parts so named in human anat: 
omy. 
171 The pupa-case is generally ornamented with golden spots; hence the 
common name chrysalis. 
172 More properly, at least in the Bee, the lip is not converted into a suc- 
torial tube, but into an extensible tongue, with which the liquid food is 
lapped up. 
173 All Vertebrates have a notochord, but not all have a vertebral column, 
as the Amphioxus. This eccentric creature, without skeleton, limbs, brain, 
heart, lymphatics, or red blood, we leave out of account. It is not fairly a 
member of the snbkingdom, but rather a link between the Mollusks and 
Fishes. In aquatic animals the posterior limbs are the ones aborted or re- 
duced, if any; in land animals the fore-limbs are usually sacrificed. The 
vertebre correspond with and are dependent on the nervous centres. This 
is shown by the fact that the tail, which is reproduced by Lizards in case of 
loss, is a single bone, because although bone may be reproduced, the spinal 
cord can not be. 
174 The smallest corpuscles are found in Ruminants; the largest in Am- 
phibians with permanent gills. The average size in Birds is double that of 
Man’s, and about equal to that of the Elephant. Those of Monkeys are a 
trifle smaller than the human. In the embryo they are larger than in the 
adult. Camels only among Mammals have oval disks. 
178 Oblong skulls, whose diameter from the frontal to the occipital greatly 
exceeds the transverse diameter, are called dolichocephalic ; and such are usu- 
ally prognathous, i. e., have projecting jaws, as the negro’s. Round skulls, 
whose extreme length does not exceed the extreme breadth by a greater 
proportion than 100 to 80, are brachycephalic ; and such are generally orthog- 
nathous, or straight-jawed. 
© The classes are variously grouped into the Hematocrya, or Cold-blood- 
ed, and the Hematotherma, or Warm-blooded; into the Branchiata and 
Abranchiata ; into the Allantoidea and Anallantoidea ; and into Ichthyopsidu 
(Fishes and Amphibians), Sawropsida (Reptiles and Birds), and Mammalia. 
