PRIVATE. Vil 
a. Anus. ri. Inner branch of appendage. 
ap. Appendage. sd. Stomodxum, or fore-gut. 
bl. Blastoderm. a. Five anterior thoracic somites. 
br. Gill. B. Antennal gland. 
cp. Carapace. y. Shell gland. 
ep. Epiblast. §.  Papilla through which the shell gland opens. 
f. Frontal sensory papilla. € Outer egg-membrane. 
h. Heart. g. Inner egg-membrane. 
hy. Hypoblast. n. Contour of body. 
i. Intestine. ge. Cellular membrane. 
I. Liver. « Muscular wall of intestine. 
1b. Labrum. Epithelium of intestine. 
m. Mouth. Dorsal organ. 
ms. Mesoblast. Appendage connected with sexual function. 
mt. Metastoma. Larval membrane. 
n, Nerve. Caudal fork. 
oc. Paired eye. Rudiment of dental apparatus in stomach. 
ocl. Unpaired eye. Communication between liver and intestine. 
pd. Proctodeum, or hind-gut. Hy podermis. 
re. Outer branch of appendage. 
SPR ar St Se 3 
The Roman numerals indicate the appendages of the body in their consecutive order. 
1-10. Development of PHytiopopa (Apus cancriformis). Figures from Cart Cuaus, Zur Kennt- 
1. 
2. 
~J 
10. 
niss des Baues und der Entwicklung von Branchipus stagnalis und Apus cancriformis. 
Abhandl. Konigl. Gesellsch. Wissensch. Gottingen, XVIII., Taf. VI.—VIII., 1873. 
Nauplius larva, on its escape from the egg, from the ventral side. Behind the mandibles (III) is seen the 
beginning of the formation of the five anterior somites. ocd, ocellus. The darker portion is the intestine. 
The same larva seen from above, the appendages removed. cp, rudiments of dorsal shield or carapace. 7, in- 
testine. J, liver. a, five anterior thoracic somites. , dorsal organ. 
Second larval stage, from ventral side. IV, first maxilla. /, frontal sense papilla. New thoracic somites have 
been added posteriorly. VI, VII, VIII, appendages of three anterior thoracic somites. £, caudal fork. 
The same, from dorsal side. 
Third larval stage, from below. 1 mm. long. The mandibles have developed a powerful cutting blade at 
their base. The rudimentary second maxille (V) have appeared, and four new thoracic appendages. 
8, antennal gland, probably homologous with the ‘‘ green gland” of Mulacostraca. 
Fourth larval stage, from below. 1 to 1} mm. long. New somites continue to form at the hinder end of the 
body, and appendages to arise from the somites already formed. There are now seventeen pairs of append- 
ages, including the three pairs of nauplius limbs, formed or in the process of formation. Behind the un- 
paired eye the paired eyes are beginning to be formed. The so-called liver forms three diverticula on each 
side of the head. , shell gland. The dorsal shield has grown backward so as to cover the four anterior 
thoracic somites. II, mandible. III’, mandibular palp. 7, labrum. 
Fifth larval stage, from below. 14mm. long. The appendages have begun to appear as far back as the nine- 
teenth (XIX), and about six somites are marked off by transverse segmentation back of this. The man- 
dibular palp is now much reduced. oc, paired eye. 
Mouth parts of the same stage. III, mandible. III’, mandibular palp. IV, first maxilla. V, second 
maxilla. 6, papilla in which the shell gland opens. 
Foot of the twelfth pair from a female larva with dorsal shield 2mm. long. r7, ramus internus, comprising 
six joints or lobes. re, ramus externus. 67, branchial sac or epipodite. 
Foot of the first pair from a larva with dorsal shield 2} mm. long. Letters as in the last figure. Through 
successive moults the nauplius appendages become atrophied, the second antenne being especially reduced 
in size, and the mandibular palp disappearing altogether. 
