416 Duplicate Twins and Double Monsters 



D. — Separation from Above Downward, and Kone from Below 

 Upwards; Components Placed Laterally. 



This series has the first five stages in common with series A, and 

 diverges from it at stage V (= D. I), beyond which A shows a separa- 

 tion from below upwards, ivliile D does not, hut continues the initial 

 separation from above doivmvards. This results in (1) a greater and 

 greater divergence of the body axes, and (2) the development of pos- 

 terior limbs in the angle between them, forming ischiopagi. This method 

 may ultimately result in separate twins as in the other series. The 

 stages, after that corresponding to A. V, are as follows : 



D. I. — This is practically the same as A. V (represented by the 

 Toccis and Eitta-Christina), but with the separation a little farther 

 down and the angle between the two trunks a little greater. The 

 amount of divergence seems a variable quantity, and in fact the bodies 

 are capable of some lateral movement. Thus, in the example of this, the 

 " Monstrum anglicum" (Pig. 2, c) the bodies are represented in a con- 

 temporaneous engraving as almost forming the same horizontal line, 

 but in the figure cited to represent the next stage (Fig. 2 a and b), the 

 bodies form a very divergent V. 



D. II. — The farther progress of the separation from above downwards 

 has produced a double rudiment of a median leg, comparable to those 

 of A. VI, B. II, and E ; or to the double median arm of A. IV, E and F. 



Ex. — Case figured by Forster, Tab. I, Fig. 15 ; after MacLauren, Phil. 

 Trans., Vol. 32. Fig. 2 a and b of this article shows a slight advance 

 beyond this. 



D. III. — Stage with the upper posterior limbs, i. e., those in the angle 

 between the trunks, separate but rudimentary. 



Ex. — An instance of this is given by Fisher, 66. 



D. IV. — Typical ischiopagi, with limbs of both sides complete, and 

 with perfect genitals and anus between them, formed by two halves con- 

 tributed by the two components. 



Ex. — Fig. 1 of this article; any typical ischiopagi. 



D. V. — Here, as in other series, may be placed separate duplicate twins 

 differing from the others merely in their mode of origin considered 

 geometrically. These, like those resulting from series C, are probably 

 a common type. 



In the lower row of the diagram are collected a few more or less unique 

 types of diplopagi, wdiich show relationship to the several series above 

 given, but which differ in extent of development of some part. They 

 are as follows: 



