SOUTH AFRICAN TERMITES. 43 



individual tracheae arise, figs. 50a, b, c (PI. VI) ; from eacli 

 pipe these grow as in figs. 41 and 42 (PI. V), and the majority 

 of them travel to the paired ovarian cords which lie within 

 the plurge. To these they attach themselves like the tentacles 

 of an octopus and form groat brushes, figs. 43a, b (PI. V). 

 This development follows a considerable distension which 

 first takes place at the junction of the three primai'y sub- 

 divisions of the pipe as illustrated in fig. 40 (PI. V). This 

 phase is succeeded by those shown in figs. 41, 42, and the 

 final nymphal form is that illustrated in figs. 43a, b; a sliowing 

 an external and b an internal view. In B are to be seen the 

 two muscles behind the spiracles, and below the ovarian 

 cord a part of the peristaltic ribbon is also shown. In these 

 figures it is seen that trachei>3 now extend down the pipe and 

 enter a short, Inroad dilatation. The transformation of the 

 spiracles has already been explained, and the disruption in 

 the case of TV to Xof the queen mentioned. Fig. 44 shows a 

 side view of one of this series of spiracles, and it will be 

 noticed that all the trachea? now open into the cup-like mouth 

 of the pipes. With disruption the valves are shredded to 

 fragments, and the trachelos or mouth of the pipe is now the 

 spiracle, the nature of Avhich is illustrated in figs. 45a and b. 

 Tracheae may be modified by the volume of the air-route. 

 In the following section, wherein an attempt is made to 

 liomologise different parts of the system, use is made of this 

 feature to explain the disguised bases of a number of palisade 

 commissures. For example, in the nascent stage whilst the 

 pipes of spiracles V to X divide into three principal stems, 

 one of these stems, instead of appearing to be a palisade com- 

 missure, seems to be the visceral, with the palisade as a 

 vertical growth therefrom. This change in the arrangement 

 (see fig. 10, PI. Ill), is due to the enlargement of the direct 

 route to the part demanding the greater supply of air. 



Ve. The Homologiks of the Main Stem. 



In figs. 18 and 19 (PI. Ill) and 20a and 20b (PI. IV), an 

 attempt is made to show the natural arrangement of the 



