NORTH AMERICAN SALMONIDAE 



243 



(Suisun Bay) and tliose for the Klamatli River. 

 These t.wo samples l)y McCire^or (1923) are the 

 highest and lowest in caecal count. I suspect that 

 this variability is caused by some extraneous fac- 

 tor. "\Mieu the Klamath River counts are sepa- 

 rated into those caught at Requa at the mouth of 



the river and those taken at the salmon counting 

 weir, 170 miles upstream at Klamathon, the weir- 

 caught salmon show a much lower count. Pos- 

 sibly, the upstream count was lowered on account 

 of the atrophy of the digestive tract prior to 

 spawning. 



Table 8. — Number of pyloric caeca in species of Oncorhynchus 



' Skeena River, British Columbia. 

 ' Quf*.*n CharlotU? Islands (7 streams). 

 3 Vancouver Island, Morrison Creek. 



* Lower Fraser River (5 streams). 



* Cowlitz River, Wash. 



* Middle Fork, Willamette River, Oreg. 

 ^ McKenzie River, Oreg. 



9 South Santiam River, Oreg. 



" Klamath River (a, at Requa, mouth of river; b, at Klamathon racks, 

 170 miles upstream). 

 '° Sacramento River. 

 1' Sacramento River. 

 i> Sacramento and San Joaquin Rivers. 



