THl'] DEVElvOl^MKNT OP PALUDINA VlVll'AKA. 119 



the origiual right. Followiug- this twist iu a series of trans- 

 verse sections a peculiar relation between the oesophagus and 

 the connectives is noticeable. In the region of the anterior 

 ganglia and for some distance behind them the oesophagus is 

 compressed so as to render its outline oblong in section. At 

 first bilaterally symmetrical, it soon becomes completely 

 asymmetrical, the long axis, as seen in section, sloping at 

 6rst upwards and to the left, then passing through the hori- 

 zontal position to slope upwards and to the right ; in other 

 words, the oesophagus apparently follows the connectives in 

 their twist, as shown in figs. 18 and 19. At the completion 

 of the twist the oesophagus becomes round in section, and 

 passes back for some considerable distance lying between the 

 two connectives, Avhich are now once more in the same hori- 

 zontal plane ; then the connectives appear to become partly 

 twisted a second time to take up the position with regard 

 to the mantle cavity posteriorly, which has been already 

 described. Unfortunately, in this region the oesophagus is 

 still circular iu section, and we have no direct evidence as to 

 whether or not it follows the connectives in the same way 

 that it does more anteriorly. 



The relations between the connectives and cesojDhagus are 

 seen to a greater or less extent in stages previous to this, but 

 the description of them has been deferred till now as being 

 easier of comprehension when they are present in such a 

 marked degree. Already in Stage C, where we first noticed 

 the tipping of the visceral hump, a slight apparent twist of 

 the oesophagus was visible ; this was more marked in the 

 following stage, and increased in each succeeding stage up 

 to the present. It is as well to notice that this condition of 

 the oesophagus was plainly visible before the visceral con- 

 nectives appeared at all. 



It has already been said that the animal has now attained 

 iu all essential particulars to the anatomy of the adult. A 

 few points, however, remain to be noticed, being for the 

 most part only further developments of processes already 

 begun. Of these the most obvious is the coiling which takes 



