30 SUMMARY OF CURRENT RESEARCHES RELATING TO 



indication of a fifth canal was present. The maximum extension of 

 this subdivision is on an average 0"126 mm. in specimens of 52-54 

 hours' incubation. As might be expected, the hning of the several sub- 

 sidiary canals is ependyma of precisely the same structure as the lining of 

 the central canal proper. The presence of these canals and the develop- 

 ment of their divisional walls alter considerably the external configuration 

 of the cord at the posterior end, causing it to become very much swollen. 



Origin of Closed Integumentary Follicles in the Bird.* — E. Ret- 

 terer and Aug. Lelievre find that the closed follicles in the proctodseum 

 of birds begin as epithelial buds. The epithelial cells are transformed 

 in part into stellate anastomosing elements (the reticulate framework) 

 and in part into free lymphocytes. 



Development of Columella auris in Greek Tortoise.f— 0. Bendert 

 finds that the auditory capsule does not take any share in forming the 

 columella in Testudo grseca. He confirms the view that the columella 

 auris in this type at least belongs genetically to the hyoid arch. 



Regeneration of Limbs in Amphibians.^ — C. Fritsch has experi- 

 mented with newts and salamanders. When the fore-limb was cut 

 across the humerus, there was normal regeneration of the fore-limb both 

 in the adult and in the larva. When the entire limb and the shoulder 

 girdle of one side were removed, there was still normal regeneration of 

 both. In some cases a certain mode of amputation was followed by 

 abnormal regeneration of particular parts of the fore or hind limb. The 

 author gives a full account of all the regenerative processes. He also deals 

 with false and rudimentary polydactylism and with super-regeneration. 



Tadpoles in Sea-water.§ — A. S. Pearse observed frogs and newly- 

 hatched tadpoles along the edge of a creek opening into Manila Bay. 

 The frogs belonged to the genus Rana. The tadpoles developed in 

 pools of slightly diluted sea-water, containing 2*096 p.c. of sodium 

 chloride, or even more. 



Thymus in Elasmobranchs.]]— J. Aug. Hammar has studied this 

 gland in various Elasmobranchs. There are four lobes on each side, 

 dorsal to the gill-clefts, in Raja radiata and R. davata, Acanthias vulgaris 

 and Spinax niger, three in Chimtera monstrosa. Apart from the absence 

 of myoid cells, the structure is essentially like that of higher Verte- 

 brates. Involution begins with the first appearance of ripe sex-cells. It 

 is marked by increased emigration and degeneration of lymphocytes, by 

 extended degeneration of reticulum cells. 



The thymus lobes in Acanthias and Spinax arise from the dorsal end 

 of the first four gill-clefts ; there is a transitory thymus bud at the fifth 

 A placode-like thickening at the spiracle may be of a thymus nature. 

 In the same types the thymus breaks through the muse, constrictor 

 superficialis arcuum visceral., and some of the muscle-fibres become inter- 



* C.R. Soc. Biol., Ixxi. (1911) pp. 390-2. 

 t Anat. Anzeig., xl. (1911) pp. 161-77 (6 figs). 

 X Zool. Jahrb., xxx. (1911) pp. 377-472 (57 figs.). 

 § Philippine Journ. Sci., vi. (1911) pp. 219-20. 

 II Zool. Jalirb., xxxii. (1911) pp. 135-80 (3 pis. and 6 figs.). 



