WITH NOTES ON THE WEST INDIAN SPECIES. 249 



In the largest specimen whose measurements are given in the above table, the 

 hepatic region commenced with about a dozen brown hepatic coeca ( which were followed 

 by a long stretch of foliaceous, dull yellowish saccules, and these again by a still 

 longer gradually decreasing series of brown lobes. The larger saccules are finely digitate 

 or crenulate at their free margins and are quite lamelliform, like the leaves of a 

 book, being extraordinarily flattened antero-posteriorly and closely crowded together. 



On the inner surface of the genital pleurae, especially towards the base, are often 

 to be observed numerous white rounded dermal islets. 



In some cases the gill-pores may be observed to be surrounded by a rim of 

 brown pigment, and fine lines of the pigment radiate out from the gill-pores to the 

 submedian line 1 in which the genital pores occur. 



The proboscis is remarkable for its small size relatively to the capacious collar 

 (PL XXVII. Fig. 6). It is probably liable to frequent injury owing to the excessive 

 boring propensities, deep down in heavy volcanic sand, which this species exhibits. 

 Specimens are often obtained in which the proboscis is quite concealed within the 

 collar without betraying any pronounced lacerated surface ; so that it probably re- 

 generates very quickly. 



The most distinctive external feature of this species is the abrupt ending of the 

 genital pleurae some distance in front of the hepatic region (PL XXVII. Fig. 6). 



The maximum development of the genital pleurae is behind the branchial region. 

 In front they become much lower as they approach the posterior rim of the collar, 

 and converge towards the middle line. The gonads commence some distance behind the 

 anterior end of the pleurae. The genital pleurae can not only meet one another in 

 the middle line so as to close in the dorsal nerve-cord and the branchial tract, but 

 they can effect a mucous junction with one another. When the animals are preserved 

 during such a mucous junction (which normally is only temporary) the mucus coagulates 

 into a dense leathery band, which is untearable. If one tries to separate the pleurae 

 by force the body-wall ruptures but the mucous coagulum remains entire. No such 

 mucous junction of the genital pleurae is effected in Pt. flava. 



Sometimes the gonaducal (submedian) line is marked out behind the branchial 

 region by a brown-pigmented groove running along the inner base of the genital 

 pleurae ; and there may also be observed fine interannular lines of brown pigment. 



The ventral middle line is conspicuous in external view by its bright red colour, 

 presumably due to the ventral blood-vessel showing through 5 . 



The dorsal blood-vessel is less conspicuous in external view. 



A colour-variation which I think is directly traceable to difference in habitat and 

 nutrition is worthy of mention. The remarks already recorded as to the colour of the 

 hepatic saccules referred to specimens obtained from the volcanic island of Matupi in 

 Blanche Bay, New Britain. Those which I obtained from a small coral island (Pigeon 

 Island) midway between Cape Gazelle and Blanche Bay had dark green liver-saccules. 



1 This is not an appropriate designation, and I think it should be replaced by some such term as 

 gonaducal line. 



- The blood of the Euteropneusta is an oxyphile non-corpusculated fluid, as shown by its intense affinity 

 for eosiu. Hence it seems probable that the red colour often observed in the region of the vascular trunks 

 in living specimens is due to a substance like haemoglobin if not to haemoglobin itself. 



35—2 



