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



1-10. Development of Amphipoda. Figures from B. Ulianin a7id Adolphe de la Valette 



St. George. 



1-7. Orclicstin. From Ulianin, Zur Entwicklungsgeschiclite der AmpliipoJeu. Zeitschr. wis.sensch. Zool., XXXV., 

 Taf. XXIV., 1881. 



1. Egg with four cleavage spheres. ^, chorion. The cleavage is superficial. In each of the four cleavage products 



is a nucleus siuTOUuded hy protoplasm (5) which sends amccboid processes out into the investing deuto- 

 plasm. These nuclei with the investing layer of protoplasm are the "amceboid cells" of Ulianin. They 

 afterwards increase by divisiou, come to the surface of the yolk, and from them is formed the blastoderm. 



2. Section through one of the cleavage spheres of the same. 5, amoeboid cell, not yet transported to the surface. 



3. Section of egg at later stage. The "amceboid cells " (S) have migrated to the periphery of the egg, divided, 



and from them has been formed the blastoderm (b I). 



4. Later stage, superficial view. The blastoderm has largely increased at the exjjense of the " aiureboid cells." 



5. Section of an egg a little younger than the one represented in Fig. 4, to show the formation of the mesoderm 



cells by division of the blastoderm cells. 



6. Section of egg at later stage, passing through the dorsal organ or " micropyle apparatus." cp, epiblast. in s, 



mesoblast. X, micropyle apparatus, arising as a patch of thickened epiblastic cells. 



Note. — Ulianin homologizes the dorsal organ of Crustacea with the shell gland of Mollusca. 



7. Section through embryo after the appeaiance of the apjiendages. X, dorsal organ. The cells have become 



invaginated so as to form a sac. dp, deutoplasm. f, yolk sphere, nc, nucleus of yolk sphere, with proto- 

 plasmic investment. 

 8-10. Gammanis pulcx. From La Valette St. George, Studien iiber die Entwickclung der Amphipoden. 

 Abhandl. naturforsch. Gesellsch. Halle, V., 1800. 



8. Egg from brood-pouch of parent, showing the enclosed embryo. All the limbs are formed before the embryo 



quits the egg. Note the ventral flexure of the embryo compared with the dorsal flexure of the Isopod em- 

 bryo (PI. VI.). X, dorsal organ, connecting the embryo with the first larval skin which surrounds the 

 whole embryo, dp, food-yolk. 



9. Portion of the dorsal surface of the same, more highly magnified, to show the connection of the embryo with 



the larval skin through the dorsal organ. After the epiblastic invagination is formed, as sliown in Fig. 7, 

 the whole surface of the epiblast secretes a thin structureless cuticula (larval membrane), which separates 

 from the underlying epiblast at all points excepting within the invagination. Here the cuticula remains 

 attached to the epiblast until the atrophy of the dorsal organ. jB, egg-membrane, a, larval skin. X, dorsal 

 organ. 



10. Portion of the upper half of the body, o c, eye. dp, remains of food-yolk, a, larval skin with the so-called 



micropyle (X) torn away from the sac of the dorsal organ (X') which lies in fourth segment of the body. 



11-19. Development of Stomatopoda. Fic/uns from Walter Faxon, Carl Clads, and W. K. 



Brooks. 



11. Youngest known stage of Stomatopod larva of the Erichthus type of development (Erichlhoidina), seen from 



below. The line on the left of the figure indicates the length of this larva. The body consists of an anterior 

 unsegmented portion bearing an ocellus (o c I), a pair of stalked eyes (n c), two pairs of .simple antennie (I, II), 

 a pair of mandibles (III) without palpi, and two pairs of maxillae (IV, V). From the dorsal side of this 

 head portion is developed a large shield or carajiace produced into a rostrum in front, and extending back- 

 ward so as to cover most of the middle or thoracic region of the body, but entirely free from the undeilying 

 segments back of the head. Behind the head is a region composed of eight segments, the five anterior of 



