THE < I i IE Mii'Di.i: C.LK.M i. i 





of its man rial i- either dinvtly or indirectly f In- i-jiit helium of the 

 l.ody cavity, as it hB b en po>Mhle to prove in many OftMfl 

 ( 'yclo>tt>m< >, Selachians, Amphihia, ami Amni' 



There are forme,!, following one another in imine i 



short fransverae tubules (fig. _''- *fi. \\hich an- at one end contiii 



with the epithelium of the L, !y i-avity, and at tlie oilier end, which 

 i"mainsfur a lu:iy tim.> c-lo-e 1, are joinei to t he m une-.hric diu-t ( 



Tig. 203. Embryo of a Dog of 25 days, straightened out and seen from in front, after B.scuorr. 



Magnified 5 diameters. 

 (/, Int-.-iin:il tube; ds, yolk-sac; al, allantois ; nn, mesonephros ; 7, tlie two lobes of the liver, 



with the lumen of the vena omphalomesenterica between them ; ve, lie, anti-rior and ixMterior 



extremities ; /,, heart; ///. mouth ; <tu, eye; y, olfactory pit. 



which runs close to them, but somewhat more laterad. The mesone- 

 phros elongates from before backward and attains a great length on 

 both sides of the mesentery, for it reaches back from the n pun of 

 the liver nearly to the posterior end of the body-cavity ; it acquin s 

 a very delicate, regular condition, as the figure of an embryo Dog 

 twenty-five days old >lu\vs (fig. 203 un), and can be designated as 

 a coinb-shnp>'d gland, composed of a lateral collecting tube, running 

 lengthwise of the body at a little distance from the mesentery, and, 



