MEMOIRS OF THE NATIONAL ACADEMY OP SCIENCES. 369 



The fourth form (after third moult). When six or seven days, old the third moult is passed, 

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

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

 short; the basal or aural spine extends to nearly the end of the first joint. The bristle-bordered 

 plate of the autenute has now developed a considerable spine near its outer extremity, a rudiment 

 of which appears in the first larva (Fig. 7). This represents the squamal spine, to which the plate 

 is ordinarily attached, in the adult. The spine is here developed from the plate. The latter may 

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

 small chela has the adult form. 



The fifth form (after fourth moult). These animals moulted the fourth time ten days after 

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

 them. 



METAMORPHOSIS OF ALPHEUS SAULCYI FURTHER ABBREVIATED. 



As was stated above, the metamorphosis of Alpheus saulcyi may be still further accelerated 

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

 in a glass dish April 25 (Fig. 17, PI. XXii). The prawn (var. longivarputs) was taken from a brown 

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

 in Fig. 15. 



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

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

 have nearly the adult form, the exopoclites of the former being rudimentary, as in Fig. 8. The 

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

 hooded, but not so much as the four-day old prawn 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 .24 



