1914.] NATURAL SCIENCES OF PHILADELPHIA. 287 



The coiled portion of the ileum terminates at the 209th gastro- 

 stege; the remainder, 9 mm. in length, is straight. 



The ileo-ccecal valve is at the 214th gastrostege. 



The ccecal pouch, 8.5 mm. long, extends from the 214th to the 

 209th gastrostege; it lies between the right oviduct and the terminal 

 straight portion of the ilemn. 



The junction of the ileum and csecum, and the csecal pouch are 

 subject to a wide range of variation in different species, and are 

 worthy of being recorded in detail. 



The posterior vena cava is anomalous owing to its large diameter, 

 which is 2.5 mm. Upon opening the coelum, just caudad to the 

 heart, this vessel appears as if it were the liver. The illusion is 

 increased as j ust posterior to the apex of the heart this vein is sharply 

 flexed towards the dorsal wall, and from below, this bend looks 

 exactly like the blunt tip of a liver. 



The external landmarks of the principal viscera in terms of gastro- 



steges are as follows: 



Per cent. 



Total number of gastrosteges 236 100 



Apex of heart 59 25 



Liver, anterior tip 78 33 



Liver, posterior end 7 147 62.2 



Gall-bladder, centre r 171 72.5 



Kidney, right, anterior tip 210 88.8 



Kidney, right, posterior end 220 93 



Kidney, left, anterior tip 216 91.5 



Kidney, left, posterior end 226 95.8 



The scale formula in this specimen is abnormal. It will be noted 

 that the first row to be added was the VI, and the first to be sup- 

 pressed was the V, and the next to be dropped was the VI. The 

 normal condition would have been for the VI to be the first sup- 

 pressed followed by the V. 



Over five hundred specimens of various species have recently been 

 investigated for this scale formula character. In the normal state, 

 when a certain scale row is added anteriorly and further along the 

 body begins to taper and a reduced count occurs, this reduced count 

 is regularly brought about by the suppression posteriorly of the same 

 scale row that was added. Where several rows are added and later 

 these are suppressed, the sequence of suppression is regularly in an 

 inverse order to that in which they appeared. 



The scale formula of a different specimen having 226 gastrosteges 

 was as follows : 



