112 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Psammodromiis, etc. The great modifications include a reduction and 

 disappearance of teeth on the palate, a flattening and weakened ossifica- 

 •tion of the skull with elongation of the rostrum and other changes, a 

 disappearance of the parietal foramen, a disintegration of the head- 

 shields and other changes in the head-scales, the formation of a 

 transparent disk in the lower eyelid and ultimate fusion of the lower 

 with the upper, the formation of a denticulation or a fringe of scales in 

 front of the ear-openings, a reduction or increase in the size of the 

 scales on the body and tail, a decrease in the imbrication of the shields 

 on the belly, a reduction and loss of the collar, a lengthening and 

 compression of the digits accompanied by an increase in the number of 

 inferior lamella, a multiplication of the scales round the digits and 

 other changes, a lengthening of the tail perhaps accompanied by an 

 increased fragility, a modification of the patterns of markings, and an 

 assumption of vivid colours. Starting from striation there was an 

 evolution on the one hand to " ocellation " (in longitudinal, irregular, 

 or transverse bars), and on the other hand to spotting (longitudinal, 

 irregular), reticulation, and barring. 



Anatomy of Blacksnake.*— W. H. Atwood gives an account of 

 the structure of the viscera of Zamenis constrictor, to which we refer 

 mainly on account of its disclosure of variability. " If the variability 

 is as great in all snakes as it is in the blacksnake, the accepted descrip- 

 tion will prove to be very inadequate, if not misleading." In a number 

 of ways the visceral structure of the blacksnake differs from what has 

 ' been described elsewhere. The left lung, inadvertently called the 

 right (p. 34), is about one-fourth of an inch long and nearly the same 

 diameter, while the right lung is some 5-6 inches long. The left lung 

 varies in size and shape in different specimens. It lies just beneath 

 the front of the heart and is connected with the trachea by a poi'e. It 

 is supplied with blood from the vessels of the right lung. The left 

 pulmonary artery and vein are absent. 



Hsemoglobin in Invertebrates.f — Isabella Leitch has made an 

 experimental study of Planorbis conieus and larv® of C/dronomus in 

 order to discover the precise function of the haemoglobin. It makes 

 available, by its power of binding oxygen chemically, a quantity of 

 oxygen sufficient for the needs of the animals at oxygen tensions so low 

 tha^ the necessary amount is not supplied by physical solution. In 

 FJanorbis the mode of action is as in Vertebrates ; it depends not at 

 all on a power of " storing " oxygen, but wholly on the constant circula- 

 tion of a current of alternately oxidized and reduced blood between 

 the lung and the tissues. In Ghironomus it is even simpler, but quite 

 similar ,\iamely, the constant binding of oxygen at the surface of the 

 body and the constant giving up of it in the interior— a continuous 

 mixing and interchange of oxidized and reduced blood kept in motion 

 by the'beating of the heart ; and the only difference is that in each case 



* Washington Univ. Studies, iv. (1916) pp. 1-38 (21 figs.), 

 t Journ. Physiol., 1. (1916) pp. 370-9. 



