1890.] 235 



the cases I have seen are very blac1\, a coloration due in all probability 

 to some mineral matter in the water whence they came. In spinning 

 up the larvae usually fix the cases gregariously to root fibres of water 

 weeds, the attachment being effected by a silken band spun round the 

 mouth end ; a slightly convex membranous operculum with a slit 

 placed towards the side closes the case. 



Oviposition takes place while the ? rests on the surface of the 

 water, and the act seems often to be the closing one of her life. The 

 ova are irregularly spherical (apparently somewhat flattened), and are 

 enclosed in a gelatinous substance which soon after contact with the 

 water swells up into a large oval or spherical mass. I am unable to 

 say what may be the normal course of the egg-mass ; those observed 

 by me seemed to be kept floating through coming in contact with 

 matter on the surface, and they were usually precipitated by accident ; 

 I think, however, that under ordinary circumstances they will sink at 

 once. (It should be remembered that examples in confinement were 

 under notice ; there may be some differences in detail under natural 

 conditions). Resting at the bottom, the mass seems to grow more 

 transparent, and on the tenth or eleventh day the embryonic develop- 

 ment must be well advanced, the eyes of the larva and the outline of 

 its body being easily made out. Three or four days later the larvae 

 are hatched, but they do not at once emerge from the gelatinous 

 envelope. The first hatched larvae lived at least two days free under 

 cover of the envelope, but immediately they emerged, cases of minute 

 sand grains were formed. A sketch of one of these larvae before it 

 had made a case is given on Plate I, fig. 11 ; the natural size of the 

 creature is a little over \ mm. 



EXPLANATION OF FIGURES (Plates I and IT). 



LARVA. 

 PL. I. 



11. Sketch of Young Larva ; natural size, a little over \ ram. 



PL. II. 



1. Mandible, left, from above (C, o. c. 1). 



2. do. do. from beneath ( do. ). 



3. Maxilla and Labium, from beneath (C, o. c. 2). 



4. Labrum from above (A, o. c. 3). 



5. Antenna ( do. ). 



NYMPH. 



6. Labrum, from above (C, o. c. 2). 



7. Mandible, from beneath ( do. ). 



8. Apex of Abdomen, from above (A, o. c. 3). 



