a 
A 
1885.] Thysiology. . 1121 
manner fused together on the median line serially and transversely. 
The actinotrichia of all the fins are accordingly represented an- 
cestrally in the slender embedded part of the parapodial sete of 
worms. 
These conclusions seem to support those of Dohrn, but also 
receive additional support from a consideration of the segmental 
organ and the way these are developed in certain worms, accord- 
ing to Hatschek, and in Chordata, according to Semper and Bal- 
four. In one other important point the primitive Chordata and 
chetopods agree, namely, in the possession of a great number of 
segments or mesoblastic somites. I therefore regard the Chor- 
data and Chetopoda as representing two divergent series. The 
former, upon the concentration of the muscular substance of the 
somites on the neural aspect of the body-cavity, and the abortion 
of the latter in the caudal region, acquired a new mode of progres- 
sion, the tail then became vertically flattened, so that the para- 
podia were thrown into two rows dorsally and ventrally, and 
finally fused as supposed above; the displacment towards the 
middle line of the rows of parapodia being greatly favored by the 
lateral movements of the tail of the ancestral form. The presence 
of the body-cavity and viscera anteriorly probably prevented the 
shifting and median concrescence of the notopodia, so that they 
remain near their original position as the rudiments of the paired 
fins. 
These views may at first seem far-fetched and improbable, but 
when I am able to present them more fully with new data and 
illustrations in a special memoir’ upon which I am now engaged, 
hope to be able to show that they lead to conclusions of the 
greatest possible moment in scientific morphology.— ohn A. 
Ryder. 
PHYSIOLOGY.’ 
Menica Puysics.3—The time has come when even in America 
it is recognized that medical education demands for a foundation 
a knowledge of those general chemical and physical laws which 
control the history of matter in all its forms. In Germany and 
France special courses in physics have long formed a part of the 
medical curriculum, and Dr. Draper has undertaken the difficult 
but praiseworthy task of preparing for the English-speaking 
Medical student a non-mathematical text-book of physics which 
shall present with tolerable completeness an account of matter 
and its laws, with special reference to their bearing on the physio- 
logical processes of the body. There are probably few scientific 
subjects in which the selection of material and the method of 
1 Studies on the development of the Chordata and Achordata, together with an 
exposition of the Archistome-theory. 
* This department is edited by Professor HENRY SEWALL, of Ann Arbor, Michigan. 
3 By J. C. Draper, M.D., LL.D. Lea Bros. & Co., 1885. 
