PLATE VI. 



a. Anus. '"'• Inner branch of .apjicnilaffe. 



ap. Appi-ndage. *■''■ StuuiudLcuni, or fcre-gut. 



bl. Blastodtrm. » Five aiiteiicr thoracic somites. 



bi: Gill. ?■ Antcnnal gland. 



cp. Carapace. y- Shell gland. 



ep. Epiblast. 5- Papilla through which the shell gland opens. 



/'. Frontal sensory pajiilla. c. Outer ogg-menibrane. 



Ii. Heart. C Inner egg-nicnibrane. 



htj. Hypoblast. 1. Contour of body, 



i. Intestine. tt- Cellular membrane. 



t. Liver. '• Muscular wall of intestine. 



lb. Labrimi. «■ Epithelium of intestine. 



m. Mouth. ^- Dorsal organ. 



m s. Mesoblast. (»■ Appendage connected with sexual function. 



m t Metastoma. '•■ Larval membrane. 



n. Nerve. J. Caudal fork. 



o c. Paired eye. "■ Rudiment of dental apparatus in stomach. 



ocL L^npaired eye. p- Communication between liver and intestine. 



pd. Proctodicum, or hind-gut. <r. Hj'podermis. 



r e. Outer branch of appendage. 



The Roman numerals indicate the appendages of the body in their consecutive order. 



1-10. Development of Phyllopod.'V (Apiis caucriformis). Figures from Carl CL.\tis, Zur Kennt- 

 niss des Btiucs iind der Eutwicklung von Branchipus stac/iialis iiud Apus cancrifurmis. 

 Abhandl. Konigl. Gesellsch. Wisseiisch. Gottingen, XVIII., Taf. VI.-VIIL, 1873. 



1. Nauplius larva, on its escape from the egg, from the ventral side. Beliind the maiidililes (III) i.s seen the 



beginning of the formation of the five anterior somites, ocl, ocellus. The darker portion is the intestine. 



2. The same larva seen from above, the appendages removed, cp, rudiments of dorsal shield or carapace, i, in- 



testine. .1, liver, a, five anterior thoracic somites. X, dorsal organ. 



3. 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, f, caudal fork. 



4. The same, from dorsal side. 



5. Third larval stage, from below. 1 mm. long. The mandibles have developed a powerful cutting blade at 



their base. The rudimentary second maxill;E (\ } have appeared, and fonr new thoracic appendages. 

 ;3, antenual gland, probably homologous with the "green gland" o{ Mitlacostraca. 



6. Fourth larval stage, from below. 1 to \\ 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 apjiend- 

 ages, including the three pairs of nauplius limbs, formed or in the process of formation. Behind the un- 

 ]iaired eye the paired eyes are beginning to be formed. The so-called liver forms three diverticula on each 

 side of the head. 7, shell gl.and. The dorsal shield has grown backw'ard so as to cover the four anterior 

 thoracic somites. Ill, mandible. Ill', mandibular p.alp. Ih, lahrum. 



7. Fifth larval stage, from below. 1 J mm. long. The appendages have bi'guu to appear as far back as the nine- 



teenth (XIX), and about six somites are marked oil' by transverse segmentation back of this. The man- 

 dibular palp is now much reduced. c, paired eve. 



8. Mouth parts of the same stage. Ill, mandible. Ill', mamlibular palp. IV, first maxilla. V, second 



maxilla. S, papilla in which the shell gland opens. 



9. Foot of the twelfth pair from a female larva with dorsal shield 2 mm. long, r >, ramus internus, comprising 



sLx joints or lobes, re, ramus extemus. b r, branchial sac or epipodite. 

 10. Foot of the first pair from a larva with doreal shield 2A mm. long. Letters as in the last figure. Through 

 successive moults the nauplius ap]iendages become atrophied, the second antennaj being especially reduced 

 in size, and the mandibular palp disappearing altogether. 



