1901. ] OF THE GEXTS BJKSTHAMIA. 195 



of the integument already referred to. It is very unusual to find 

 so few — and those such thin — septa dividing the anterior segments. 

 Their arrangement, moreover, is very puzzling when taken in re- 

 lation with the external segmentation and with the location of 

 organs internally. The first recognizable septum is fairly thick 

 and separates segments v. and vi. Its insertion on the body-wall 

 corresponds quite accurately to the external furrow separating 

 those segments. There is then an apparent gap of considerable 

 extent in which there are no septa at all, though the oesophagus 

 and the gizzards are bound to the parietes by a few muscular threads. 

 The next actual septum is very thin ; it is inserted behind the last 

 of the two gizzards on to the alimentary canal, but to the body- 

 wall at about the middle of the ixth segment, as mapped by the 

 dorsal pores which are quite conspicuous from the inside of the 

 body. It might therefore be held that the few muscular strands, 

 already referred to, represented the otherwise missing septa vi. \ii. 

 and vii./viii.. and perhaps viii. ix. Obvious though this determi- 

 nation seems on a dissection, it is apparently not correct. If we 

 count the septa from a fixed point such as the segment lodging, 

 and containing the external orifice of, the anterior spermiducal 

 gland, we rind that up to as far forwards as the xivth segment 

 there is a correspondence between the insertion of the septa and 

 the segments which they demarcate. Between the septum which 

 defines the fifteenth segment anteriorly and the second recogniz- 

 able septum just described, I find six septa crowded together. It 

 seems to follow therefore that that septum, in spite of the place of 

 its attachment to the body-wall, is really septum vii. viii. and that 

 the only really missing septum is vi./vii. 



As this latter septum would if present lie between the two 

 gizzards, it is not surprising to find it absent, a state of affairs which 

 is very characteristic of the gizzard segments of Perichasta (syn. 

 Amyntas and Pheretima). 



None of the septa as already mentioned are particularly thick ; 

 those dividing segments xii./xvii. are the most developed. 



Alimentary Canal. — The pharynx occupies the first five segments 

 of the body. The two ijizzanls are separated by a very short tract 

 of thin-walled oesophagus. The anterior of the two gizzards is 

 really preceded by a third rather rudimentary gizzard, for the walls 

 of the end of the oesophagus are nearly as thick as those of 

 iln' gizzard and are divided from it by a brief thin-walled region. 

 From what has been Baid with regard to the septa of tin's pari of 

 the body, it Bhould he dear that the two fully developed gizzards 

 lie in segments vi. and vii.. a quite reasonable determination of 

 their situation. Segments v. and vi., however, are more usually 

 occupied by the gizzard- in this genus. The calciferous glands are 

 in tegmenta xv., xvi., and xvii. The firs! pair differ Prom t he rest in 

 being whiter in colour. Each gland is Bomewhal kidney-shaped 

 but with a number of trans> erse depressions dividing it into lobules. 

 The glands open separately into the oesophagus, by wide ami easily 

 visible ducts, 



13* 



