MEMOIKS OF TOE NATIONAL ACADEMY OF SCIENCES. 369 



The fourth form (after tliird moult). — When six or seven day-s old the third moult is passed, 

 but only slight changes are introduced. The small chela ami the inner and outer antenme of this 

 phase are given in Figs. 9, 10, 16, PI. xxil. The inner branch of the antennules is still relatively 

 short; the basal or aural si)ine extends to nearly the end of the tirst joint. The bristle-bordered 

 plate of the antenuai has now develoi)ed a considerable spine near its outer extremity, a rudiment 

 of which appears in the tirst larva (Fig. 7). This represents the squanial spine, to which the [ilate 

 is ordinarily attached, in the a<lnlt. The spine is here developeil from the plate. The latter iiTay 

 disapiiear, as we shall see further on, to be finally regenerated from the base of the spine. The 

 small chela has the adult form. 



'I'he fifth form (after fourth moult). — These animjvls moulted the fourth time ten days after 

 hatching. Very liltle change was apparent, except in size, and beyond this point we did not follow 

 them. 



METAMOKPnOSlS OF ALPHKHS SATILCYl FirRTHER AHBRKVIATED. 



As was stated above, tiic metaiiiorpiiosis of Alphiux xautcyi may be still further accelerated 

 80 as to practically disappear altogether. This fact is illustrated by a young Alpheus hatched 

 in a glass dish Ai)ril L'.'i (Fig. 17, PI. XXII). The prawn (var. longicar2}us) was taken, from a brown 

 sponge. The eggs, half a dozen in luimber, were slow in developing. The small chela is shown 

 in Fig. 15. 



This phase corresponds with that usually attiuned after the second moult (shown in Fig. 8, 

 PI. XXI), with which it corresponds in size, and color. All the thoracic and abdominal appendages 

 have nearly the adul.t foi'in, the exoiiodites of the former being rudimentary, as in Fig. 8. The 

 large chela is most i>rominent, being nearly as large again as the smaller one. The eyes are partly 

 hooded, but not so much as the four-day old jirawn represented by Fig. 3. The Alpheus had to be 

 held in a compressorium in order to be drawn, so that the parts are slightly distorted by pressure. 

 At the time of hatching most of the hairs on the appendages generally are in a rudimentary 

 condition. 



S. Mis. 94 ^4 



