which are jirovuled each with a pair of two-branclied swimming appendages, the three posterior being desti- 

 tute of limbs. The five pairs of swimming legs represent the five pairs of grasping legs or maxillipeds of 

 the adult stomatopod. (These are homologous with the three pairs of maxillipeds and two anterior pairs 

 of legs of the Dccapoda.) The three following segments, which are without limbs, are the three posterior 

 thoracic somites of the adult, which are destined to bear the three pairs of ambulatory limbs. The posterior, 

 broad, uiisegmented tail represents the long segmented abdomen of the adult. The specimen here figured 

 ■was on the point of moulting and within the anterior part of the tail plate are seen two abdominal segments 

 which will become free after the moult. The posterior border of the tail of the next stage is also seen 

 through the transparent cuticle, a, anus. On either side of the auus is seen a coecal, glandular body. 

 From a sketch by Faxon, made at Newj)ort, E. I., August 23, 1876. 



12. Part of the border of the tail fin of the same, more highly magnified. In the next stage known, the two 



abdominal somites seen within the telson in Fig. 11 become free, and the anterior one develops a pair of 

 rudimentaiy bilobed appendages. These appendages are the first abdominal. The first pair of antenn;e 

 become two-branched. As the development proceeds the inner branch of the second ])air of maxillipeds 

 increases in size and acquires a terminal claw, while the outer branch is aborted. The abdominal somites 

 and appendages develop gradually in succession from before backwards. 

 13-16. From Claus, Die Metamorphosen der Sijuilliden. Abhandl. Kiinigl. Gesellsch. Wissensch. Gottingen, XVI., 

 Taf. II., III., 1871. 



13. Older Erichthoid larva (Erichlhoidina spinosa) of 7 mm., lateral view. Both pairs of antennte are now fur- 



nished with a lateral branch. The first and second maxillipeds (VI, VII) have lost their external branch 

 and approximate the form of the same parts in the adult. Gill-plates have developed from the basal joint of 

 each (not shown in the figure). The three following pairs of limbs have become much reduced in size. The 

 abdomen now consists of the full number of somites, each with its pair of appendages (XIV-XIX). The 

 last pair (XIX) is very small. 



14. Older stage {Erichthoirlinn armala), seen from the ventral side. 9 mm. long. The three posterior pairs of 



maxillipeds (VIII-X) have undergone atrophy, being now' reduced to mere rudiments. The three posterior 

 thoracic segments are still without a trace of appendages, n, abdominal nerve-cord. 



15. Still older form, or Erichthus stage {Erkhthus Edimrdsi), 16 mm. long, from the Indian Ocean. The three 



posterior pairs of maxillipeds (VIII-X) have again gi'own out in their permanent shape, and behind them 

 each of the three posterior segments of the thorax has developed a pair of small buds (XI-XIII), the first 

 rudiments of the three pairs of ambulatory appendages of the adult. The third flagellum of the first antenna 

 is present. VIl', gill-plate attached to base of the large grasping leg (VII). 



16. Later or Squillerichthus stage (Squillerichthus triangularis) of a Stomatopod from Zanzibar. The three pairs 



of ambulatory appendages are much enlarged and two-branched. On the five anterior jiairs of al)douiiual 

 limbs are seen the nidiments of gills. The sixth abdominal appendage has now outgrown the others and 

 has its permanent form. 



From Claus's observations it is probable that the larv.-e of the Erichthoid type of development belong to 

 the genus Gonodactylus. 

 17-19. Development ai Squilla cmpusa, from Beaufort, N. C, to illustrate the Aliina type of Stomatopod develop- 

 ment. From Brooks, The Larval Stages of Squilla, cmpusa Say. Chesapeake Zoological Laboratory, 

 Scientific Results of the Session of 1878, PI. IX., X., 1879. The outline of Fig. 18 is corrected after a 

 drawing of the same stage by Alexander Agassiz. 



17. Youngest stage observed, magnified about 75 diameters, seen from below. This is probably the stage in which 



the larva leaves the egg. (Cf. Paul Mayer, Mittheil. Zoolog. Stat. Neapel., II. ji. 219, who has seen an 

 Alima larva come out of the egg of a Squilla, probably -S'. mantis. ) This stage corresponds in a general sense 

 to the stage in the development of the Erichthus type where the three postpiior ])airs of maxillipeds have 

 atrophied (fig. 14). There are no two-branched swimming-feet on the thorax, and no thoracic limbs of any 

 kind back of the great grasping legs or second maxillipeds (VII), although three free somites are present. 

 The three posterior thoracic somites are represented by a long uusegmented region. The abdomen has five 

 segments and the terminal fin, the four anterior segments carrying swininiing-feet (XIV-XVII), represented 

 only on one side of the figure, n, nerve-cord, ocl, ocellus. 



18. Next stage observed, ventral view. All the thoracic segments are now present. 



19. Older stage, ventral view. The ocular .segment has become marked ofT at the front end of the body. Tlie six 



posterior pairs of thoracic limbs (three posterior pairs of maxillipeils and the three ambulatoiy limbs of the 

 adult) have begun to form as minute buds (VIII-XIII). The fifth pair of abdominal limbs (XVIII) is 

 present in a very rudimentary condition, and the nerve-ganglion of the sixth abdominal somite is seen, 

 although the somite itself is not yet freed from the telson. 



