1892. J OFTHE GENtS PERICH.ETA. 171 



The atrium is not provided with a terminal sac ; the glandular 

 part of each atrium is very extensive, and reaches from segment xvii. 

 to segment xxii. 



Between the opening of the atrium and tl)e nerre-cord on each 

 side of the body are three small white oval glands {p.g-, fig- 6, 

 Plate X.), which correspond to the papillae visible on the exterior of 

 the xviiith segmeot. 



Note on a Perichaetayrom Singapore. 



I received a single specimen of this Perichata in a living condition 

 from Kew Gardens ; it had reached there in a Wardian case from 

 Singapore. 



Unfortunately I omitted to make any notes upon the worm 

 while alive ; a quantity of other material which came about the 

 same time oblijied me to preserve h at once for future study ; the 

 specimen was killed in Perenyi's solution and investigated by 

 means of transverse sections. It is very possibly the same species 

 as that which I have called Peiichceta morrisi, and descrihed in the 

 present paper ; but my notes upon its diagnostic characters are so 

 iar from being complete, that I do not venture to express an opinion 

 as to the name which should be applied to it. 

 It measured 2| inches when preserved. 



The cliteUum occupied the usual three segments, but I am not 

 certain as to whether setse were, or were not, present. 



On the xviiith segment was a single median /7api/Za placed between 

 the two atrial pores. 



I observed the gizzard to occupy the usual position and that 

 caca were present. There are two pairs of spermatJiecce in segments 

 \i. and vii. ; these agree very closely with those of Perichceta morrisi 

 in the proi)ortions of the appendix to the spermatlieca, but the 

 extremity of the former was swollen, forming an oval sac. 

 This is possibly merely due to the presence of more sperm in one 

 case than in the other. 



I desire to call special attention to the structure of the atria. 

 These organs have the usual form characteristic of the genus 

 Perichceta. 



Their minute structure, however, presents one character of some 

 little interest, which has not yet been recorded in the genus. 

 Transverse sections through the stout muscular duct by which the 

 fecretions of the glandular part of the atrium reach the exterior 

 show that the muscular sheath encloses three separate ducts instead 

 of only one, as is the case in all other species which have been as yet 

 investigated microsco|dcally. One of these tubes is large and is the 

 main conduit of the secretion of the gland ; the two other tubes are 

 equal in size to each other, but very much smaller than the main 

 tube. 



The smaller tubes retain their distinctness from the larger 

 tube until near the external orifice, though still remaining enclosed 

 within the same muscular sheath. Just before the external aperture 



