388 
has likewise no bearing on the point, as, in these 
circumstances, the animal will not rise’ to the surface 
and use its lungs at more frequent intervals than 
animals placed under normal conditions. Mr. 
Boulenger stated that up to a certain point only could 
the shrinking gills and fins of the animal be made 
to undergo renewed development (when transferred 
from shallow to deep water). 
Homology of the Gills. 
Prof. H. Braus described the results of a number 
of transplantations carried out on tne larve of Rana, 
Hyla, and Bombinator by Dr. Ekman. The gill- 
ectoderm was detached before the gills had formed, 
and was transplanted to some other parts of the tad- 
pole. Such gill-ectoderm gave rise to gill-filaments, 
but not to gill-clefts; circulation of the blood was 
also wanting, and the filaments soon perished. If 
the gill-ectoderm was raised, turned round through 
180°, and replanted on the same area, gill-filaments 
were formed with circulation and gill-clefts, the latter 
being turned 180° from the normal position. It is 
concluded, therefore, that the ectoderm alone is able 
to produce gills, and determines their position and 
form, but the further development of the gills is 
dependent on the ingrowth of mesoderm (vascular 
system). ‘Foreign’? ectoderm, i.e. ectoderm which 
under ordinary circumstances does not develop gills, 
behaves differently according to the part of the 
organism from which it is taken. That taken from 
the trunk or the dorsal part of the head and planted 
in the position of the gill-ectoderm does not give rise 
to gills, but if ectoderm be taken from the region 
above the embryonic ‘heart and transplanted to the 
position of the gill-ectoderm, there are formed gill- 
filaments and clefts as in the normal animal. It is 
not yet certain what factors induce this ectoderm to 
imitate the gill-ectoderm, but Prof. Braus regards this 
imitation as of fundamental importance in relation to 
theories of homology. 
Cultures of the Embryonic Heart. 
Prof. Braus exhibited by the microkinematograph 
the beating heart of a tadpole (6 mm. long), which 
had been in the culture-medium seven days when the 
photographs were taken. He demonstrated the regu- 
lar rhythm, about eighty beats per minute, the sus- 
pension and irregularity due to the chemical rays of 
light, also typical “refractory’’ periods, and _ the 
rowth of the pigment cells. At this period of 
evelopment the heart has no ganglion cells and 
nerves are not present, nor are muscle-cells distin- 
guishable; it seems therefore that the protoplasmic 
links between the cells must be the conductors of the 
stimuli which pass along the heart. 
Phylogeny of the Carapace and Affinities of the 
Leathery Turtle. 
Dr. Versluys directed attention to the special char- 
acters exhibited by the carapace of the leathery turtle 
(Dermochelys coriacea), pointing out that in other 
Testudinata the carapace is formed by a relatively 
small number of plates firmly united to the vertebrz 
and ribs, but in Dermochelys the carapace is composed 
of a number of small thin plates, forming a mosaic, 
separated from the inner skeleton by a thick cutis. 
Dermochelys is not primitive, for its cervical vertebra 
show that it is derived from a Cryptodiran ancestor. 
That this ancestor possessed the typical carapace is 
shown by the fact that parts of it are still found in a 
reduced state in Dermochelys represented by the 
deeper or ‘‘thecal’’ layer of the dermal skeleton. 
Prof. Dollo has maintained that the ‘epithecal"’ 
skeleton is a new formation, but Dr. Versluys is in- 
NO. 2300, VOL. 92] 
NATURE 
[NOVEMBER 27, 1913 
* 
clined to assume that, in the ancestors of the Testu- — 
dinata, there were rows of epithecal elements (though — 
feebly developed) beginning in the neck ond continu- — 
ing over the thecal shell’to thé base of th. ‘ail, and — 
that the ancestors of Dermochelys reduced their heavy — 
thecal shell and replaced it by the new mosaic shell — 
formed by a proliferation of the marginals and other 
epithecal elements. ; 
Prof. Dollo discussed Dr. Versluys’s conclusions, 
and stated the reasons which led him still to regard 
the mosaic carapace of Dermochelys as an entirely 
new structure. He held that a study of fossil Chelo- 
nians permitted no other interpretation. He did not 
consider Archelon (Upper Cretaceous) as an ancestor 
of Dermochelys, but rather Eosphargis (Lower 
Eocene), because of the nature of the plastron. 
In reply Dr. Versluys said that whether or not 
Archelon was an ancestor of Dermochelys, both 
possessed an epithecal mosaic carapace, of which the 
marginals formed part. 
Unilateral Development of Secondary Male Characters 
in a Pheasant. 
Dr. C. J. Bond exhibited the skin of the white- 
ringed Formosan variety of the Chinese pheasant, 
the plumage on the left side of which was roughly — 
that of the adult male. The left leg showed a spur, 
but there was no spur on the right leg. The white- 
ringed neck feathers occurred in a half-circle on the 
left side only; the wing primaries and coverts were 
female in character, except for a few male feathers 
on the left side; the tail coverts were of the male 
type. 
left side, and a sexual organ was in the usual position 
of the left ovary, but sections showed that it consisted 
of ovarian elements undergoing pigmentary degenera- 
tion and testicular elements in active growth. Dr. 
Bond pointed out that such a case presented a diffi- 
culty if the ordinary or hormonic explanation of the 
origin of secondary sex characters were accepted. 
He suggested that two factors at least are concerned 
in the origin and development of secondary sex 
characters: one, a gametic factor—the primary sex 
gland, and the other a somatic factor, and that the 
two factors may vary independently of each other 
under certain conditions of abnormal hereditary 
transmission. 
A Mammal-like Dentition in a Cynodont Reptile. 
Dr. W. K. Gregory exhibited, for Dr. R. Broom, 
upper and lower jaws of a small species of Diadem- 
odon, from a study of which Dr. Broom concludes 
that the Cynodonts had deciduous incisors, deciduous 
canines, and four deciduous premolars, exactly as in 
mammals. As there is no evidence, in any specimen, 
of a dental succession after maturity has been 
reached, he concludes that the two sets of teeth corre- 
spond to the mammalian milk set and permanent set. 
Notharctus, an American Eocene Lemur. 
Dr. W. K. Gregory exhibited a skeleton of Noth- 
arctus rostratus, an Eocene lemur, the discovery of 
several partial skeletons of which in Wyoming, by 
the American Museum of Natural History, affords 
material for a fairly complete knowledge of the skull, 
dentition, limbs, and vertebrae. The material shows that 
Notharctus is a primitive lemur, more primitive than 
any now living, and possibly ancestral to the Indrisine 
lemurs. The correspondence in the details of limbs, 
&c., between Notharctus and modern Lemuridz is 
remarkably close, but the front teeth of the former 
are more primitive and have not assumed the lemurid 
characters; the molars are in pattern ancestral to 
those of Propithecus. 
A well-developed oviduct was present on the ~ 
