BIOLOGY. 279 



LIMBS OF MAMMALIA. 



Dr. Burt G. Wilder, in the "Memoirs of the Boston Society of 

 Natural History," has brought prominently to view the remarkable 

 relatit)ns existing between the anterior and posterior regions or 

 poles of the vertebrate body, both as exhibited in the structure of 

 the bones and muscles of the limbs, and the more general rela- 

 tions found in the body itself and the internal organs. The prin- 

 ciple of antero-posterior symmetry or " longitudinality " seems to 

 be characteristic of vertebrates, and has not been observed among 

 other animals. According to this law, the anterior and posterior 

 poles of the vertebrate body have organs and parts that are hom- 

 ologous and morphologically identical, although teleologically 

 very different, while the corresponding parts on opposite sides are 

 both morphologically and teleologically repetitions of each other. 

 The body is divided into four regions, the thorax and head cor- 

 responding to the abdomen and pelvis. Some of the correspond- 

 ing parts are as follows: " In the anterior region, enumerating 

 from above, that is from the vertebi-al column downward, the nose 

 or anterior nares, the upper lip, the mouth, the tongue, and the 

 chin ; posteriorly, the anal opening, the perinasum, the vaginal 

 opening, the penis or clitoris, and the pubes." There are two 

 principal diverticula of the alimentaiy canal, the lungs and the 

 urinary bladder ; the former open forward and the latter back- 

 ward, and their outlets are between the pharynx or mouth and the 

 tongue anteriorly, and the vaginal opening and the clitoris poste- 

 riorly. " The thyroid gland is in relation with the larynx much 

 as the prostate gland is with the neck of the bladder." The heart 

 is considered only a more or less complicated enlargement and 

 convolution of the great arterial trunk. The anterior limbs are 

 shown to be appendao'es of the basal segment of the skull, thrown 

 backward by growth in the higher vertebrates, but occupying their 

 morphological position in fishes and some young animals. 



ORIGIN AND DEVELOPMENT OF ANIMAL LIFE. 



Prof. H. J. Clark, in his work entitled " Mind in Nature," has 

 fully discussed the various modes of reproduction, and increase 

 among animals, the origin and early condition of ovarian eggs, 

 and the changes they ungergo as development i^roceeds. The 

 egg, considered as the lowest condition of animal life, is shown 

 to consist at first of a mere spherical aggregation of albuminous 

 and oily matt-ers, like a simple cell, but with a bipolar character ; 

 i. e., the albumen concentrates at one side of the spherical mass, 

 and the more oily portion of the yolk on the opposite side. 

 While the eggs of infusoria never attain a more complicated 

 structure than this, in those of higher animals a further change 

 takes place, resulting in the formation of the so-called germinal 

 vesicle and germinal dot, which is to be considered only a con- 

 tinuation of the process commencing with the imperfect separa- 

 tion of the albumen from the oily portion in the lowest form of 

 the egg, the diiierence being only in degree, and not in land. 



