Bd. V: 6) THE FISHES OF THE SWEDISH SOUTH POLAR EXPEDITION. 



55 



Short notes on the morphology of the digestive system of 



Notothen iidœ. 



The shape and arrangement of the intestinal organs is rather similar in all the 

 members of this family examined. 



The Hver is often large. Its main mass lies to the left, constituting a very large 

 and long lobe, which often as in Trematoinus Iiansoni georgianus extends back- 

 wards almost to a level with the anal opening. The shape of the liver of this fish 

 is represented in fig. 2 in ventral aspect. The meeian portion often forms one or 

 two short lobes and the right portion is represented by 

 narrow lobe quite anteriorly. This organ seems, how- 

 ever, to be subject to a considerable individual variation 

 as in some specimens of this same fish the viscera were 

 much more broadly covered by the liver than in the one 

 figured. The same organ of other members of this fa- 

 mily has about the same shape although the large left 

 lobe does not extend quite so far back, almost two 

 thirds of the distance to the anal opening or more in 

 Cliampsocephalns giainari, Nototlimiia gibberifrons and 

 tessellata, somewhat less still in Notothenia macrocepliala 

 marmorata, coriiceps etc. and Harpagifer. In Para- 

 chœnichthys the liver is very large extending two 

 thirds to the anus and the mass corresponding to the 

 left lobe expands also beyond the median line towards 

 the right side. 



The size of the ventricle is considerable and when 

 it is filled with food it has been found to extend all way 

 to the posterior end of the abdominal cavity in several different species belonging 

 to difïerent genera of NototJieniidœ. Already this faculty of dilatation indicates that 

 these fishes possess ventricles of the caecal type, to use Owen's nomenclature. In 

 Nototlienia gibberifrons this type is perhaps least differentiated of the species exa- 

 mined in this respect. Its ventricle has when moderately expanded the cardiac and 

 fundus-portivns not much wider than the pylorus-portion. The latter is directed 

 forwards. In other species of Nototlienia {tessellata, coriiceps, macroceph. marnio- 

 rata) the general arrangement is the same, but the fundus-portion forms a larger 

 cul de sac. In Tretiiatouius haiisoni georgianus the pylorus-portion branches of at 

 ringht angle and the cœcal type is thus more differentiated, as fig. 3 shows. In 

 Champsoceplialus gnnnari the fundus-portion forms a still wider and larger cul de 



Fig. 2. 



