148 DR. W. B. BKNHAM ON [Feb. 16, 



tinctly marked off from the clitellum, are more sharply separated 

 from one another than is the case elsewhere in the body. The 

 histological structure of the tubercula is represented in Plate VIII. 

 fig. 14. 



On each side of somite xiii., between the outer and inner couples 

 of ohaetffi, and rather nearer to the former, is a copulatory papilla, 

 similar to those I have described above for M. papillata. 



The nephridiopores and the oviducal pores have the usual positions ; 

 I could not detect any other apertures. 



The chsetas have the same arrangement and markings as in M. 

 papillata : they are longer than in that species and commence on the 

 second somite. 



The annuli of the anterior somites are extremely well marked by 

 deep grooves (Plate VII. fig. 6). The first somite is simple; the 

 second is triannulated ; the third is biannulated ; somites iv. to ix. 

 (inclusive) are triannulated, the third annulus in each case being 

 very distinctly marked off; the tenth is biannulated ; the following 

 ones are bi- or triannulated, though the annuli are not so distinctly 

 separated. 



Of the internal organs, one or two features are worthy of note. 

 Three septa are stronger than the others ; the first lies between somites 

 iv. and v., the second strong one lies in the middle of the somite 

 viii., the third in the middle of somite ix. 



The oesophageal glands are nipped by the septum between 

 somites ix. and x., as in M. beddardi. There is only one pair of 

 ciliated rosettes (and probably, therefore, of testes) in somite x. and 

 one pair of sperm-sacs in the same somite. 



In M. beddardi, also, there is but a single pair of each of these 

 organs — the testes in somite x., the sperm-sacs in somite xi. 



I traced the sperm-duct as far as somite xvi., where it enters the 

 muscles of the body-wall. But I have been unable to determine the 

 position of the external aperture ; for I did not wish to injure the 

 single specimen. 



In M. rappi the spermducal pore lies in somite xx. ; but I was 

 unable to find the pore in M. beddardi, where, however, it has 

 probably the same position'. 



The spermatheccB are eight in number, arranged in couples on 

 the anterior margin of each side of somites xii. and xiii. ; they are 

 larger than in M. papillata, though of the same shape. In number 

 and position they agree with the condition in M. beddardi. 



The four species of Microchasta can thus be arranged in two 

 groups : — 



I. M. rappi and M. papillata have two pairs of testes, and 

 very numerous spermathecse arranged in rows of several in a 

 row ; the oesophageal glands lie wholly in one somite ; the dorsal 

 vessel is doubled in each of the somites v. to ix. 



II. M. beddardi and M. belli have but oae pair of testes ; have 

 eight spermathecse arranged in couples ; the oesophageal glands are 



^ In M. benhami this pore is between somites xx. and xxi. 



