SCOTTISH TARDIGRADA, COLLECTED BY THE LAKE SURVEY. 651 



all the dorsal processes, and is the most reduced condition yet seen. Another series of 

 variations of the same species has as its principal peculiarity the forking of seta d. 

 This may be forked from the base or from some distance above it (fig. 3) ; the branches 

 may be equal, or one may be a short, thick spine and the other a long seta ; the seta d 

 of one side may be forked and the other undivided ; and lastly, as in the other series, 

 all the processes may be reduced to spines, the second dorsal to a triangle, and the seta 

 b as well as all dorsal processes may be lacking. Truly a remarkable range of variation 

 if all really belong to one species ; and if not, we have, following the old rule, a con- 

 siderable number of species, all built on the same lines, and differing only by the 

 processes. I prefer to regard the processes as somewhat variable in number. 



The five commonest lateral processes, which Professor Richters distinguishes by 

 the letters a to e, are indicated by the letters in the figure of E. islandicus (Plate I. 

 fig. 4a). Many species possess all five processes, either as setae, spines, or knobs, and 

 many lack all of them except the first. This first seta, a, between the first and second 

 segments, is present in every known species of Echiniscus. The other lateral processes 

 are also intermediate between the other segments, except e, which springs from the slit 

 separating the lobes of segment VI. 



Larvce. — It is highly probable that all species of Echiniscus have only two claws in 

 their earliest stage. In all species of which the larva is known this is the case. When 

 a species is found in abundance and can be well studied, there is usually little difficulty 

 in finding some larvae. It is therefore curious that the two-clawed larvae of E. reticu- 

 latus have never been seen, though the species is very abundant in some lochs, and 

 individuals of various sizes have been found, some very small ones laying eggs. 



Two-clawed larvae of the undernoted species are known : — E. arctomys, E. mutabilis, 

 E. gladiator, E. islandicus, E. testudo, E. granulatus, E. quadrispinosus, E. 

 oihonnse, E. blumi, E. merohensis, E. duboisi, E. wendti, as also of several species not 

 yet described. 



E. arctomys, Ehr. (3). 



Segment V is distinct from VI, and forms a half-ring. In E. mutabilis, and most 

 of the other species which have V separate, it has a pair of plates. 

 The two-clawed larva has been found in Loch Morar. 



E. mutabilis, Murray (6). 

 Two-clawed larva, Loch Morar. 



E. islandicus, Richters (18). (Plate I. figs. 4a to 4c.) 

 Description. — Very large; 12 main plates, 3 pairs and 3 median; V paired, first 

 and second median each divided into two parts ; VI deeply 3-lobed. Lateral processes 

 5 ; a and e very long setae ; b, c, and d short curved spines. Dorsal processes ; short, 

 tooth-like spines on posterior border of II, III, and IV ; a pair of large broad spines on 

 V, near the middle line. Two small spines on the lateral lobes of VI. Fringe of sharp 



