PLATE IX. 
a Anus tb. Labrum. 
a6. Abdomen. oc. Compound eye. 
cp. Carapace. ocl. Simple eye. 
ct. Cuticle. pl. Procephalic lobe. 
dp. Deutoplasm. Ub Rostrum. 
im Frontal sensory organ. a, Tail fold. 
fs Intestine. A. Dorsal organ. 
1. Liver. 
The Roman numerals signify the consecutive order of the appendages. 
1-10. Development of Scuizorova, continued (Mysis). Figures from Evovuarp Van BENEDEN 
and P.-J. VAN BENEDEN. 
1-6. Mysis ferruginea. From Edouard Van Beneden. 1-3, Recherches sur la Composition et la Signification 
bo 
de Gui, Pl. X. Mém. Cour. Acad. Roy. Belgique, XXXIV., 1869. 4-6, Recherches sur I'Embryo- 
genie des Crustacés. II. Developpement des Mysis. Bull. Acad. Roy. Belgique, [2.] XXVIIL., Pl. IL, 
1869. 
. Egg showing the commencement of partial segmentation. 
. Later stage in the segmentation. The blastoderm now forms a zone of small extent at one pole of the egg. 
. The blastoderm has extended over the whole surface of the yolk. On the ventral side the cells have a roundish 
form, while on the dorsal side they are very much flattened. 
. Later stage. pJ, anterior expansion of the ventral side of the blastoderm to form the procephalic lobes. 
a, fold of the blastoderm which separates the hinder portion (@ d) of the embryo from the anterior section of 
the body. 
- Later stage. The embryo is now ready to leave the egg. The three nauplian appendages, two pairs of anten- 
ne, and mandibles (I, II, III) are present, and the embryo is invested with a delicate cuticle. \, dor- 
sal organ. While within the egg, it will be observed that the body has a ventral flexure, as in Decapod 
Crustacea. 
6. Embryo after it is freed from the egg-membranes. The body now assumes a dorsal flexure. 
7-10. Mysis chameleo. From P.-J. Van Beneden, Recherches sur les Crustacés du Littoral de Belgique. Mém. 
fe 
8. 
Ge 
Acad. Roy. Belgique, XXXIII., 1860. 
It has been seen by the previous figures that the Mysis embryo leaves the egg with three pairs of appendages 
like a nauplius. The larva undergoes its further development within the incubatory pouch of the parent. 
The nauplius skin is not discarded, but accommodates itself to the growth of the larva, forming a protective 
case, within which the young Jfysis develops. In the species here figured, the nauplius skin terminates in 
a pair of setiferous appendages. Within the nauplius skin, the larva has become provided with the full 
number of cephalo-thoracic appendages in the form of simple buds. These afterwards assume the schizopo- 
dous character, the abdominal appendages appear, and the segmentation of the body sets in. 
Larva just after the nauplius skin has been cast off, much less enlarged than the preceding figure. The 
stalked eyes (0c) are now conspicuous. They have developed from the procephalic lobes of the embryo. 
The full number of abdominal appendages (XIV —XIX) is now seen, the posterior pair largely developed. 
Later stage, shortly before leaving the ineubatory pouch of the parent. 
10. Appendages from the first to the fourteenth (first abdominal) inclusive, to show the double nature of the 
ll- 
11. 
12. 
13. 
appendages. 
11-21. Development of Pennus. Figures from Fritz Mttuer and Cart Cravs. 
16. From Miiller, Die Verwandlung der Garneelen. Arch. Naturgesch., XXIX., Taf. II., 1863. 
Nauplius stage of a Penews, from Desterro, Brazil. .4 mm. long. 
Older stage (metanauplius), seen from the side. .5 mm. long. The carapace (cy) has commenced, a large 
labrum (74) is present, together with the rudiments of four pairs of appendages (two pairs of maxilla and 
two pairs of maxillipeds) behind the nauplian appendages. A short forked tail has also formed. 
Third pair of nauplius appendages of a somewhat older stage. At its base is seen the rudiment of the masti- 
catory mandible of later stages. 
