236 D. J. SCOURFIELD ON EPHIPPIA OF LYNCEID EXTOMOSTRACA. 



reduced in length, but it is very much tliickened and highly 

 refractive. The ventral margin consists for a considerable 

 distance of the old shell margin, owing to the line of separation 

 between the ephippium and the anterior ventral portions of the 

 valves not running back much beyond the blunt angulation in 

 the middle of the ventral edge of the shell. The new edges 

 are bordered by minute elongated pieces of chitin loosely con- 

 nected together, showing that a special line of weakness is 

 developed before the moulting of the ephippium. The shell is 

 somewhat darkened, but the hexagonal markings remain as in 

 the parthenogenetic female. Around the egg are a series of 

 irregularly folded and crumpled delicate membranes, and it was 

 proved that these really form a closed envelope by the fact that 

 when an egg was crushed the contents were confined within a 

 definite area, and could only be squeezed out beyond the limiting 

 membrane by severe pressure. It is not usual in this species to 

 find the anterior ventral portions of the shell still connected with 

 the ephippium, but in the specimen figured they were so attached, 

 and looked somewhat as if they might serve the purpose of rudi- 

 mentary hooks. A front view presented the appearance shown 

 in Fig.* 32. 



I have already given an account of some observations made on 

 the repeated formation and moulting of ephippia by isolated 

 specimens of this species (9), but it will be useful to refer to 

 the subject again. Two females with resting eggs in the ovaries, 

 and having outlines like that shown in Fig. 34 {i.e., with the 

 evenly arched dorsal contour broken posteriorly by a straight 

 line), were selected for observation. In three days both had 

 moulted, and appeared as in Fig. 33 — i.e., as ephippial females. 

 After another three days both had moulted again, and appeared 

 as at first, but the resting eggs had not been extruded from 

 the ovaries and the ephippia were empty. Exactly the same 

 processes were repeated a second time in two consecutive periods 

 of three days each, after which no change was observed for some 

 time, and the observations were suspended. It is possible that 

 the inability of the animals to place eggs in the ephippia was due 

 to the absence of a male. 



This is another of the species in which I have actually seen the 

 ephippia attached in numbers to the sides of a glass jar in which 

 the animals had been kept. 



