191-1.] NATURAL SCIENCES OF PHILADELPHIA. 293 



There are three embryos; these extend from the 118th to the 

 178th gastrosicge. The growth of the anterior one has been aborted, 

 evidently owing to pressure. The middle one has a yolk sac 25 mm. 

 long, on the dorsal and anterior surface of which is coiled the embryo. 

 The head is free, being beneath and anterior to the coils. The pre- 

 vailing condition is for the head to be in the centre of the coils, where 

 it is more protected. The total length of the embryo, when uncoiled, 

 is about 45 mm. The tail measures 2 mm., which is longer propor- 

 tionately than in the adult. Each rudimentary hind limb is free; 

 it is held at right angles to the body and measures .5 mm. in length. 

 The yolk sac of the posterior embryo measures 36 mm. 



A Avell-nourished fat-hody lies between the bend in the oesophagus 

 and the first embryo. 



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



steges are as follows: 



Per cent. 



Total number of gastrosteges 194 100 



Apex of heart 60 30.9 



Liver, anterior tip 78 40.2 



Liver, posterior end 113 58.2 



Gall-bladder, centre _ 116 59.8 



Kidney, right, anterior tip 172 88.7 



Kidney, right, posterior end 181 93.1 



Kidney, left, anterior tip 178 90.8 



Kidney, left, posterior end 185 95.2 



In these three species a comparison of the position of the viscera 



in terms of percentage down the spinal column may be presented: 



Species. — 



Ilysia Cylindrophis Cylindrophis 

 scytale. rufus. maculatus. 



Sex. Female. Male. Female. 



Spinal column 100 100 100 



Apex of heart 25 29 31 



Liver, anterior tip 33 36 40 



Liver, posterior end 62 63 58 



Gall-bladder 72 68 60 



Kidney, right, tip 89 85 89 



Kidney, right, end :. 93 92 93 



Kidney, left, tip 91 87 91 



Kidney, left, end 96 94 95 



To obtain this data the number of the gastrostege underlying a 

 given anatomical point, counting from the first shield in the neck, 

 is noted. This number is then divided by the total number of 

 gastrosteges in the specimen, thereby giving the position in terms 

 of percentage. 



