450 F. A. I'OTTS. 



gaster maupasi is shown in A, Text-figure 4. Departure from 

 this type was found, however, in almost every other specimen 

 examined. Below are given some of the clearest cases of 

 variation observed in dealing with a comparatively small 

 number (about forty) of males. 



(1) There should be normally a pair of papillae situated 

 exactly opposite the anterior end of the copulatory spicules. 

 One of the most frequent and easily demonstrated variations 

 occurs when one of the pair (or very rarely both) is shifted 

 forward a smaller or greater distance. So marked a case as 

 fig-, c was observed two or three times. 



(2) A pair of papillae (4-4') occurs a short distance 

 posterior to the anus. Only small variations in position were 

 recorded here, but on one occasion a duplication of the 

 papilla of one side was observed (fig. d). ('i'he papilla of 

 the other side was seen on altering the focus, so it was quite 

 evident that the twin papillae belonged to the same side.) 



(3) In the position of papillae 5 and G there is rather 

 frequent variation ; they are sometimes nearer together, 

 sometimes further apart. Occasionally it may be seen (when 

 the animal is lying on its back) that the papillae of the two 

 sides (5, 5', and G, G') have a tendency to alternate in position 

 (fig. B shows this, but not very well). An example like fig. b 

 was observed once, in which one of the papilla?, either 5 or 6, 

 was duplicated on both sides, and the twin papillae then 

 shifted apart. 



(4) The three small papilla? at the root of the tail (7-9) 

 are rarely replaced by two. 



It is only occasionally on examining these animals that a 

 frontal view is obtained, showing the rays of the bursa on 

 both sides. In side views it is often difficult to correctly 

 observe the position of the papilla?. On this account only a 

 few definite cases of variation are referred to above. They 

 were observed in dealing with forty to fifty males. 



The accessory piece of the spicular apparatus varied in 

 form in nearly every individual. Three types are figured. 

 The first shows the most typical, in the shape of a right- 



