DEVELOPMENT OF THE PORBEAGLE SHARK. 



167 



IV. Internal Structure. 



A full account of the internal structure of Lamna embryos 

 can be obtained by reference to Lohberger (4) and Shann (6) ; 

 thus it will be necessary here to give only a summary of the 

 outstanding features of the alimentary system, together with 

 certain corrigenda of previous statements. Text-fig. 2 is 

 reproduced from Lohberger to illustrate my description of the 

 alimentary system. 



On dissection the outer skin in the abdominal region is found 



Text-figure 2. 



py- 



'%mi^ 



py.o. 



Alimentary canal of Lamna embryo (after Lohberger). 



a»., anus; b.d., bile-duct; e.g., cardiac portion of stomach (" yolk-stomacli ") ; 

 oe., cesophagns ; pt/., pylorus ; p^.o., origin of pyloric portion; pi/,s., pj'loric 

 portion of stomach; r.d., rectal diverticulum; s.i., spiral intestine; sp., 

 spleen ; v., blood-vessels. 



to be underlain by a thin layer of muscle, which is continuous 

 with the lateral muscle of the trunk. The cavity within is a 

 normal coelom. The greater part of the coelom is occupied by the 

 swollen cardiac portion of the stomach, which in an embryo of 

 350 mm. had a volume of 150 c.c. ; it is this organ, in fact, which 

 causes the great ventral distension of the body-wall alluded to 

 above as the " paunch." The wall of the cardiac stomach is 

 richly supplied with blood-vessels. (The statement in my previous 

 paper that the yolk " found its way into every interstice of the 

 body-cavity, investing completely the abdominal organs " is, of 



