732 Transactions of the Society. 



a dull yellow behind the girdle; but these colour distinctions are 

 not of importance seeing that they vary greatly with food, habitat, 

 season, and other conditions. The worm is active, and but for the 

 opaque white spot near the middle, revealing the presence of eggs, 

 it might easily be mistaken at first sight for a large Nematode. The 

 setae, however, are soon discovered when it is placed under the 

 Microscope, and the presence of setae immediately enables one to 

 differentiate it alike from Nematodes and from minute larvae of 

 Diptera and other creatures. 



As the setae are an important feature I may add that I gave 

 them special attention, since it was this character which enabled 

 me at once to distinguish it from another form (Enchytrsms hya- 

 linus Eisen), which it somewhat resembles in other respects. 

 Michaelsen's diagnosis gives the setae as equal, but the term must 

 be interpreted in relation to the setae of Fridericia. In the latter 

 cjenus the setae are often of different lengths in each bundle, but in 

 Enchytrmus they are equal. I find, however, a difference in the 

 length of the setae of E. minimus Bret, in different parts of the 

 body, and the number of setae also varies. Thus, the dorsal setae 

 are two in number in front of the girdle, and three in the hinder 

 segments, while the ventral setae number three throughout. The 

 first segment (peristomium) has no setae, the girdle segment lacks 

 the ventral setae, while the extreme posterior may also be destitute 

 of them. Now the two pairs of dorsal setae on the girdle segment 

 are small, and if their length is represented by 4, that of the front 

 segments will be 8, and that of the hinder 9. In other words the 

 posterior setae are slightly longer and more slender (as 9 : 8) than 

 the anterior, while the latter are double the length of those on the 

 girdle. It is possible that these details are liable to slight varia- 

 tion, but these are my results. (Plate XXVIII. fig. 1.) 



Next to the setae, perhaps the peptonephridia or salivary glands 

 are the most striking object. In no worm which I have ever 

 examined has the similarity between salivary glands and nephridia 



EXPLANATION OF PLATE XXVIII. 



Pig. 1. — Diagrammatic representation of: — 1. Girdle segment with two pairs of 

 short dorsal setse and male pores (mp.). 2. Segment v. with two pairs 

 of dorsal setae and triplets in ventral bundles. 3. Posterior segment 

 with four bundles of triplets. Ratios 4, 8, 9. 



,, 2. — Showing branching of blood-vessel in anterior segments of Enchytrxus 

 minimus Bret, (the blood is white). 



„ 3. — Segments iii.-vi., to show peptonephridia (p) and spermatbecae (sp.) open- 

 ing into intestine (int.). These organs are paired. 



,, 4. — Sketch of Fridericia peruviana. The hatched lines indicate such portions 

 of the vascular system as were made out. br. brain ; ph. pbarynx : 

 gl. perhaps copulation gland (unpaired) on segment 5 ; sept. gl. septal 

 gland in segments 5-7 ; s.g. salivary glands, uubranched and seeming to 

 be attached behind in segment 7 ; dil. enlarged vessels in segments 

 7, 8, 9 ; pr. prostomium. No setrc shown. 



