20 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
secondary segmentation, which gives rise to an anterior cephalic tract 
which is a region sui generis. The author traces the development of 
the neuromeres, compares the structures of the segments of the brain 
with those of the spinal cord, and notes the relation of the neuromeres 
to the sensory and motor nerves, to the mesodermal somites, and to the 
visceral arches. Dr. Neal thinks that the most important conclusion to 
which he has been led by his studies is that there is a serial homology 
between preotic and postotic segments in the Vertebrate head. The 
reason for this is to be found in the unbroken continuity of the postotic 
and preotic neuromeres ; their exact similarity on the grounds of rela- 
tions with nerves, somites, and visceral arches ; and, thirdly, the distri- 
bution of postotic fibres to preotic musculature. 
Genital Ducts of Teleosteans.* — Herr G. Schneider has studied the 
development of the genital ducts in Cobitis taenia and Phoxinus laevis. 
The oviducts arise from nephridial funnels in the same manner as the 
Mullerian ducts of other Vertebrates. The vasa deferentia are homo- 
logous with the oviducts, and, like them, correspond to the Mullerian 
ducts in other types. In respect of this homology between vasa 
deferentia and oviducts, the Teleosteans are primitive. Schneider is 
also inclined to derive the central testicular canal in higher Vertebrates 
from the cavity of the testes in Teleostei, which, again, is homologous, 
with the ovarian cavity. 
Larval Development of Amia calva.j — Mr. Bashford Dean has an 
interesting paper on the larval development of Amia calva. He describes 
the habits of tho larvm, the typical stages from the second day before 
hatching to the end of the fifth week, and some features of the organo- 
geny. The larvae of the fifth week, though scarcely an inch long, have 
practically attained their adult conditions, even as to fins, scales, and 
teeth. 
In the aquarium, the newly hatched fish remain inactive for several 
days lying on their side, attached to the floor by the sucking disc. Before 
the end of a week they have become restless, and in the second week (in 
natural conditions) they attend the male in immense swarms. There is 
ground for believing that the guardian’s care of the young lasts for about 
four weeks. 
Passing over the author’s description of the larvae of successive days* 
we shall note a few of his results as regards organogeny. 
The formation of the mouth differs little from that in Lepidosteus . 
sturgeon, and Telcosts. At no time do the appearances add evidence to 
the view that the mouth is of gill-slit origin. 
The anus is formed about the beginning of the second day ; a hint 
of a proctodaeum occurs ; throughout the early stages in the growth 
of the tail region there is no trace of a neurenteric canal, the neural 
axis being solid to begin with. 
The author gives a careful account of the origin of the liver as a 
broad dorsal fold of the gut, and amplifies his previous notes on the 
relation of yolk-sac to gut. Jungersen’s results as to the pro- and 
mesonephros are virtually confirmed. 
Brain and spinal cord originate from a solid ectodermic thickening ; 
* Mem. Acad. St. Petersb., ii. (1895) 20 pp. and 2 pis. 
t Zool. Jal.rb. (Abth. Syst.), ix. (1896) pp. 639-72 (3 pis. and 17 figs.). 
