which are provided each with a pair of two-branched 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 Decapoda.) 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, unsegmented 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 anus is seen a cecal, glandular body. 
From a sketch by Faxon, made at Newport, R. I., August 238, 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 
rudimentary bilobed appendages. These appendages are the first abdominal. The first pair of antenne 
become two-branched. As the development proceeds the inner branch of the second pair 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 Squilliden. Abhandl. Konigl. Gesellsch. Wissensch. Gottingen, XVI., 
Tate MS ue ls rl 
13. Older Erichthoid larva (Zrichthoidina spinosa) of 7 mm., lateral view. Both pairs of antenne 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 (Hrichthoidina armata), seen from the ventral side. 9mm. 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. , abdominal nerve-cord. 
15. Still older form, or Erichthus stage (Zrichthus Edwardsi), 16 mm. long, from the Indian Ocean. The three 
posterior pairs of maxillipeds (VIII-X) have again grown 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. VII’, 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 pairs of abdominal 
limbs are seen the rudiments 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 larve of the Erichthoid type of development belong to 
the genus Gonodactylus. 
17-19. Development of Sqwilla empusa, from Beaufort, N. C., to illustrate the Alima type of Stomatopod develop- 
ment. From Brooks, The Larval Stages of Sguwilla empusa Say. Chesapeake Zoological Laboratory, 
Scientific Results of the Session of 1878, Pl. 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., Il. p. 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 Hrichthus type where the three posterior pairs 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 Jong unsegmented region. The abdomen has five 
segments and the terminal fin, the four anterior segments carrying swimming-feet (XIV-XV1I), represented 
only on one side of the figure. 2, nerve-cord. oc/, 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 off at the front end of the body. The six 
posterior pairs of thoracic limbs (three posterior pairs of maxillipeds and the three ambulatory limbs of the 
adult) have begun to form as minute buds (VITI-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. 
