338 SECTIONAL TRANSACTIONS.— D. 



In Dipnoi and Elasmobranchii the mouth is opened by the action of the Genio- 

 ooracoideus or Genio-thoracicus. 



In Ganoidei the mouth is opened by the action of the Genio-branchialis and Rectus 

 cervicis. In Lepidosteus and Teleostei the Genio-branchialis is absent and its place 

 is taken bj^ the Intermandibularis posterior (Siluroids) or by the Protractor hyoidei. 



In Amphibia and Sauropsida the mouth is opened by the Depressor mandibalse. 

 In Amphibia this muscle is a secondary stage of the Levator hyoidei. In Siren and 

 Ichthyophis only a partial transference of insertion takes place, and both a Levator 

 hyoidei and a Depressor mandibulse are present. 



A Levator hyoidei is present in Dipnoi, where it is separated from the dorso- 

 anterior part of the Constrictor hyoideus. In Amphibia only the ventral part of the 

 Constrictor hyoideus is present (Interhyoideus posterior). 



In Sauropsida the Constrictor hyoideus is developed in its whole dorso-ventral 

 extent. Its dorso-anterior fibres form either a Levator hyoidei and a Depressor 

 mandibulae (Sphenodon, some Lacertilia, CrocodOia, Birds) or only a Depressor 

 mandibulse (Chelonia, Ophidia). 



The Levator hyoidei is present in embryonic, stages of all Mammalia. It either 

 persists as such (Monotremes) or develops into the Stapedius (higher Mammalia). It 

 does not develop into the secondary condition of a Depressor mandibulae. 



In Monotremes the mouth is opened by the Detrahens mandibulae, in higher 

 Mammalia by the Digastricus mandibul«, which is formed by fusion of the Interman- 

 dibularis superficialis and the whole or a part of the Interhyoideus, 



Miss D. E. Sladden. — The Adaptation of Alytes to Warmth. 



The Midwife toad (Alytes obstetricans) under normal conditions spends the greater 

 part of its life on land, living in underground holes during the day, and becoming 

 active at dusk, when it leaves its retreat to search for food. Occasonally during these 

 nocturnal ramblings it takes to the water. 



If the larvae are kept in a higher temperature than that to which they are accustomed 

 in their normal environment — from an early stage in their development — the meta- 

 morphosed young, when kept at the same temperature will frequently repair to any 

 water available. By subjecting the young toads to dry as well as warm conditions, 

 they can be forced to enter the water even during the day. 



This experiment, which induces Alytes to change its habits, appears to be most 

 successfully carried out on the young larvae, the adult toads not being able to survive 

 the violent change of temperature. 



Miss D. E. Sladden. — The Production of Defects in the Frog. 



Eggs of the common frog (Rana temporaria) when subjected to the action of 

 various agents such as sugar — which may possibly act as an absorbent of oxygen 

 in solution — or exposed to a reduced air pressure at an early stage in development, gave 

 rise to tadpoles showing various defects. 



These defects were of the following nature : — 



(a) Distention of body-cavity ; 



(6) Rupture of gut-wall caused possibly by the absorption of water and consequent 

 swelUng of the yolk, which extruded into the body-cavity ; 



(c) Flexure in tail due to a defect in the myotomic formation ; 



(d) Distortion of sacral region in the metamorphosed frogs resulting from the 

 defect in the tail : 



(e) Suppression of hind limb due to compression at an early period of development. 

 The larvae showing defects at the time of hatching, in most cases with extreme 



abnormabties, died after a short period of larval life, and only apparently normal 

 larvae remained. From among these, however, after a period of 8 weeks or over, 

 tadpoles showing flexure in tail and various consequent distortions in the region of the 

 sacrum commenced to appear. These later larvae were successfully reared through 

 metamorphoses. 



Prof. J. Graham Kerr, F.R.S. — John Samuel Budgett, a Bristol 

 Naturalist. 



