ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 557 



Modern Study of Heredity.* — Angel Clallardo gives a clear account 

 of the general scope of recent researches on heredity, with particular 

 reference to biornetrical and Mendelian studies. 



Experiments on Tadpoles. f — E. Goggio has made a series of re- 

 markable experiments on toad tadpoles. Thus a larva 3-6J mm. in 

 length may be cut into two parts, which continue to live and develop in 

 the water, independently of each other, for many days. One decapitated 

 larva lived for fifty-four days. The most striking fact is that normality 

 of development seems to be so slightly affected by the most serious 

 injuries. 



Male Mitochondria in Fertilized Ovum.J — Fr. Meves submits more 

 evidence in support of his conclusion that the chondriosomes (mito- 

 chondria and chondriokonts) represent a primitive and hereditary sub- 

 stance in the cytoplasm. They are seen in male and female germ-cells 

 and in all embryonic cells. They form the primordial substance for the 

 most diverse differentiations. The chondriosomes of embryonic cells 

 appear to be derived from both the germ-cells. Those of the male germ- 

 cell occur as individualized components in the fertilized ovum. 



b. Histology. 



Development of Dentine in Mammals. § — 0. Heinrich has made a 

 study of the development of the teeth in Mammals from the earbest 

 rudiments to the perfect teeth. He used for his investigation the em- 

 bryos of pigs, sheep, dogs and cats, and compared the corresponding 

 stages in each form. He thus summarizes the results of his investiga- 

 tion, which dealt specially with the development of the dentine and its 

 relation to the fibrils in the pulp : — The fibrils grow from the connective 

 tissue, which surrounds the primordia of the tooth, into the papillae till 

 they reach the epithelial layer. There their ends form a lattice-work 

 that becomes more and more intertwined. During this time the peri- 

 pheral connective-tissue cells of the tooth papilla become transformed 

 into odontoblasts. The odontoblasts form the basal substance of the 

 dentine which they lay down, by means of the odontoblast fibres, on 

 the network. The fibrils are separated from their network by the 

 odontoblast layer, and lie under the odontoblasts, within the pulp, in 

 which they gradually disappear. 



Regeneration of Bone in Birds, jj — Jan Kinel removed pieces of bone 

 from the skull, the keel and the fingers of adult pigeons, and observed 

 the ensuing regeneration. In the case of skull it was clearly seen that 

 the new bone developed exclusively from the adjacent periosteum and 

 from the dura mater. Similarly in the case of the sternum, the repara- 

 tion was made by the adjacent periosteum. The new growth was more 

 intense the further the wound was from the margin. Kinel cut off a 

 piece (15 mm. in length) from the second phalanx of the second digit, 



* Las Investigaciones modernes sobre la Herencia en Biologia. Cordoba, 1909, 

 72 pp. t Atti Soc. Tosc. Sci. Nat. Pisa, xxv. (1909) pp. 21-58. 



1 Anat. Anzeig, xxxvi. (1910) pp. 609-14. 

 § Arch. Mikr. Anat., lxxiv. (1909) pp. 781-811 (2 pis.). 

 || Anat. Anzeig., xxxvi. (1910) pp. 515-21 (2 figs.). 



