352 G. E. GATES. 



necessary to discontinue the work. Some of the data accumulated 

 are of such interest, however, as to warrant publication in a pre- 

 liminary note. At the first opportunity the experiments will be 

 resumed. 



In the preliminary series of operations worms belonging to 

 nearly all of the species occurring in Rangoon were anaesthetized 

 and the anterior ends excised at various levels. Only individuals 

 of two species, Pontoscolex corethrurus, and Perionyx excavatus 

 survived more than five days after the operation. At the end of 

 two months only a small amount of segmentally undifferentiated 

 tissue had been produced at the cut ends of worms of the first 

 species, whereas all operated specimens of the second species had 

 regenerated, in much shorter time, segmentally differentiated an- 

 terior ends. Further experiments were confined to this second 

 worm. 



Adult specimens of P. excavatus attain a length of 130 mm., 

 and a diameter of 5 mm. The prostomium is large, fleshy, and 

 characteristic. The intersegmental furrows are deep and clearly 

 marked. Secondary annulation is lacking. The dorsal and lateral 

 parietes are heavily pigmentecl. The clitellum is ring-shaped, yel- 

 lowish or gray, contrasting sharply in color with the non-clitellar 

 segments, and lies between the intersegmental furrows 12/13 and 

 17/18. The setae are numerous and arranged in a closed ring 

 around each segment behind the first metamere. The spermathe- 

 cal apertures are large paired pores in the intersegmental furrows 

 7/8 and 8/9 (paired spermathecae in viii and ix). The single fe- 

 male pore is clearly visible on xiv (paired ovaries in xiii). The 

 larger male apertures are closely approximated mid-ventrally on 

 xviii (paired prostates in xviii, paired seminal vesicles in xi and 

 xii, paired naked testes in x and xi). 



Mature worms can be secured in large numbers all the year 

 round. They easily adjust themselves to the conditions of life in 

 the laboratory, and have an exceedingly low mortality rate after 

 operation or injury. The sharply delimited clitellum and large 

 sexual apertures enable rapid determination of position, while the 

 clear cut intersegmental furrows, the absence of secondary an- 

 nulation, and the distinctly projecting setal circles, render segment 

 counting simple, and the detection of metameric and setal anoma- 



