hall: mesonephros and mullerian duct in amphibia. 37 



and raised in captivity. Although well fed, these were shorter by about 

 ten millimetres at the time of their metamorphosis than those which 

 were not kept in captivity. This difference in size is already observable 

 at the time when the Mlillerian duct begins to develop. For this reason 

 the length of the specimen has little significance. In the case of ani- 

 mals raised in captivity the fundament of the duct first appears when 

 they have reached a length of thirty-five millimetres ; in the others, 

 when they are about forty-five millimetres long.^ 



Some of my specimens were given me by Professor J. S. Kings! ey, 

 who also loaned me some of his slides. I wish here to express my grati- 

 tude for his kindness, and that of Doctors F. D. Lambert, H. V. Xeal, 

 and J. H. McGregor, who also put their material at my disposal. 



My anuran material consists of specimens of Rana sylvatica Le Conte, 

 which w^ere all raised from the egg. The eggs of this species can be 

 distinguished from those of any other l!^ew England anuran by the early 

 date at which they are laid. They are deposited quite as early as those of 

 Amblystoma punctatnm and are often found with the eggs of that species 

 in cold shaded pools, where they are attached in a similar manner to 

 twigs, etc. The jelly in which they are imbedded forms rounded masses 

 of a tougher consistency than the egg masses of any other New England 

 frog. The development of the Miillerian duct was also investigated in 

 Hyla versicolor Le Conte. The larvae were collected at Wood's Hole, 

 Mass., in July and kept in captivity. They are distinguished from 

 other tadpoles by their crimson tails and blunt snouts. 



I tried a number of killing reagents. The most serviceable one for 

 the younger stages seems to be a saturated aqueous solution of corrosive 

 sublimate with five per cent acetic acid. Kleinenberg's picro-sulphuric 

 mixture gave good results when the embryos were imbedded in paraffin 

 soon after hardening. By far the best results with embryos from ten 

 millimetres up were obtained with Zenker's fixing reagent. Unfortu- 

 nately this was not learned early enough to try it on younger stages. 

 Felix found it unsuitable for trout which still had the tissues loaded 

 with yolk and this might also prove to be the case with amphibian 

 material. I kept some of the hardened embryos in 82 per cent 

 alcohol, some in 90 per cent. After five or six months I was much 

 chagrined to find that none of the material so preserved except the older 

 larvae was of any value for finer details. I hear from various sources the 



1 Thinking that I might be dealing with two different specieg, I took ore of the 

 smaller larvae which had metamorphosed to Mr. Samuel Garman. He tells me that 

 he sees no reason to doubt that it is a specimen of Amblystoma punctatum. 



