^m NOTES AND COMMENTS 3 



The Lepidosiken of South America 

 At the last meeting of the Cambridge Philosophical Society on 

 December 6, Mr J. Graham Kerr gave a short account of his recent 

 expedition to the interior of the Gran Chaco of Paraguay for the 

 purpose of investigating the habits and development of Lcpidosiren 

 paradoxa. It will be remembered that Mr Kerr was aided by a 

 grant from the Balfour fund, and was accompanied ])y Mr J S 

 Budgett of Trinity College. ' ' 



Lepidosiren occurs in considerable quantity in the swamps 

 towards the centre of the Gran Chaco boreal. It is sluggish in 

 habits, wriggling slowly about among the thick vegetation of the 

 swamp. At short but very irregular intervals it visits the surface 

 and takes a breath of air. Its food consists mainly of lar^e 

 Ampullarias and masses of confervoid algae. The youn- are to 

 a greater extent vegetable feeders than'' are the adults' Lepi- 

 dosiren makes a burrow in the ground at the bottom of the swamp 

 and lines it with soft grass. In this the eggs are laid. The 

 papillae on the hind limb of the male grow out into long filaments 

 during the breeding season, and during life these are blood-red in 

 colour. Lhey appear to be ornamental structures. 



The eggs are very large— about 7mm. in diameter. Coelomic 

 eggs have a thick gelatinous coat: in fertilised and developing eg^s 

 this becomes thin and horny. Segmentation is during its later 

 stages holoblastic and unequal. Gastrulation takes place in a 

 manner which recalls that of Urodele Amphibia, and of Cyclo- 

 stomes. Eventually a tadpole larva is hatched out. This develops 

 large external giUs and a very large sucker of the Amphibian type 



The external gills and sucker disappear about six weeks afte'r 

 hatching. At the same time the colour of the young Lepidosiren 

 becomes much darker and the animals become much more lively 

 m their habits. For the first ten to twelve weeks of their free exis- 

 ence the young do not eat but live on the yolk in the walls of 

 their intestine. 



A remarkable habit of Lepidosiren was observed, namely, that 

 their normally very dark colour becomes nearly white during the 

 mght. The black chromatophores shrink up during the hours of 

 darkness— large yellow chromatophores, which are also present 

 remaining expanded. ^ ' 



During the dry season the Lepidosiren retreats into the mud in 

 which It remains breathing by means of an air-hole until the waters 

 return and set it free. 



Mattees Molluscan 

 The fourth and last note by Mr Pelix Bernard on the development 

 and morphology of the hinge in bivalve Mollusca has just been 



