TUBIFEX. 335 



of Tubifex rivulorum, and he definitely states that the 

 brain in this region is devoid of processes or lobes. He 

 figures, however, postero-lateral lobes from which well- 

 developed muscles pass to the body wall, and these lobes 

 can be clearly seen (PL I, fig. 1, ps.L), but I have never 

 been able to find the muscles. Beddard described, in his 

 definition of this species, a median, smaller, posterior lobe 

 corresponding to the anterior one ; but this I have never 

 been able to see. It is particularly easy to see the outline 

 of the brain just at this point, as the dorsal vessel runs 

 under it here, and the red colour of the blood in this 

 vessel causes the brain to show sharply outlined against 

 it. In addition to the lobes already mentioned, there are 

 yet two more to be noted, and these are very important, 

 as it is from them that the peripharyngeal connectives 

 arise. They are situated between the antero-lateral lobes 

 and the postero-lateral lobes, and are slightly more 

 ventral in position than either of these. They pass 

 obliquely outwards, downwards and backwards, and 

 finally bend sharply inwards, terminating in the nervous 

 bands known as peripharyngeal connectives which finally 

 unite, in the median line ventrally, with the first ganglion 

 of the nerve cord known as the sub-pharyngeal ganglion 

 (PL II, fig. 8 sp.g.). 



Cerebral Nerves. I have been able to recognise 

 three pairs of these, two pairs arising from the brain 

 proper and one pair from the peripharyngeal connectives. 

 Of these three pairs of cerebral nerves, one pair arises 

 from the median anterior lobe of the cerebral ganglia. 

 They really originate as one nerve forming a continua- 

 tion of the median lobe, but this condition only obtains 

 for a short distance, as the single nerve soon divides into 

 two brandies which diverge from one another. Both 

 branches, however, pass forwards towards the tip of 

 w 



