TRANSACTIONS OF SECTION D. 605 
like shape, the cement organs forming a conspicuous tubercle on either side, with 
a deep cup-like depression at its apex, and the external gills assuming a pinnate 
character. As development goes on the cement organs come to be situated on 
the upper lip, one on either side. The tail of the larva is purely diphycercal. As 
regards the internal features of development, the following details may be specially 
mentioned. The ‘swim-bladder’ develops as a mid-ventral diverticulum of the 
pharyngeal region, exactly as a typical lung. The excretory organ of the larva is 
a pronephros with two tubuies on each side. The nephrostomes in the specimens 
so far examined are in the region of metotic myotomes one and four. When at 
its maximum of functional activity the pronephros becomes a remarkably bulky 
organ, its bulk being due for the most part to the anterior part of the archinephric 
duct becoming greatly enlarged and thrown into complicated coils. In the 
30 mm. larva, obtained by Budgett on a previous expedition, the anterior tubule 
is to a great extent degenerate, though it is still distinctly recognisable in the 
sections. 
On the whole, the most striking features of the development of Polypterus 
are the extraordinary resemblances to the development of Dipneumonous Dipnoans 
and Amphibians. 
It is proposed to publish a detailed account of the developmental phenomena in 
the Budgett Memorial volume, which is now in course of preparation. 
(ii.) Notes on the Development of Phyllomedusa hypochondrialis (Daud). 
By E. J. Bugs. 
In material for the study of Anuran development collected by the late 
Mr. J. S. Budgett and handed over to me, the most complete of the series of 
stages of forms with large eggs is that obtained in South America of P. hypochon- 
drialis, a Hylid. The study of this material was therefore commenced on this 
form, with the help of Budgett’s description, already published,” and of his series 
of sections. I can confirm all his recorded observations, including that of the 
remarkable ridge formation externally in the early embryo in the branchial region. 
The ridges are formed by the pushing out of the mesenchym and ectoderm over the 
surface of the long endodermic gill pouch. The ridges visible externally behind 
the optic vesicles are, therefore, not the branchial arches, but mark the position of 
the future clefts, while the depressions on either side of the ridges mark the posi- 
tion of the branchial arches. At this stage the branchial region is spread out flat 
over the surface of the yolk, and the resemblance to an early embryo of Acipenser 
is, as Budgett pointed out, very great. As he remarks, the absence of a great 
cement organ on the mandibular arch does not obscure the likeness. I find, how- 
ever, that: at a later stage, just before hatching, paired cement organs are present, 
as vestigial organs, disappearing immediately after hatching without having 
become functional. This fact is significant; it shows that P. hypochondriahs 
must be descended from a form which, like our European Ayla, was hatched as 
a heavily yolked larva and hung from its cement organ until the yolk was 
absorbed. As the Anura which follow this course all develop from eggs with a 
relatively small amount of yolk, it follows that the resemblance of Phyllomedusa 
embryos to those of Acipenser is due to a comparatively recent increase of the 
proportion of yolk in the egg, the resemblance being, therefore, secondary. If this 
view is correct, it will be of great interest to compare the development of other 
Hylid frogs with that of Phyllomedusa, in order to determine how development is 
influenced in closely related forms by the relative amount of yolk in the egg. The 
cement organs undergo a remarkable modification just before hatching takes place. 
The clear outer ends of the columnar cells become very much swollen by an 
accumulation of secretion, and at the same time other gland-cells dorsal to each 
cement organ assume the same appearance. The swellings produce an elevated 
area of ectoderm, which extends upwards on either side of the mouth. The whole 
arrangement vanishes when the tadpole is hatched, The position of the two 
! Q.J.M.S8., vol. xlii. 1899, p. 317. 
