Pe PAWIU EieaViclile 
a. Anus. oc. Eye. 
ap. Appendage. ocl. Ocellus. 
61. Blastoderm. a. Larval skin. 
dp. Deutoplasm. B. Egg-membrane. 
ep. Epiblast. 8 Ameeboid cell. 
i. Intestine. e. Segmentation cleft. 
ms. Mesoblast. ¢. Yolk sphere. 
n. Nerve. A Dorsal organ. 
ne. Nucleus. 
The Roman numerals indicate the appendages of the body in their consecutive order. 
1-10. Development of Ampuiropa. Figures from B. Uniantin and ApoLpHE DE LA VALETTE 
Sr. GEORGE, 
1-7. Orchestia. From Ulianin, Zur Entwicklungsgeschichte der Amphipoden. Zeitschr. wissensch. Zool., XXXV., 
Taf. XXIV., 1881. 
1. Egg with four cleavage spheres. $8, chorion. The cleavage is superficial. In each of the four cleavage products 
is a nucleus surrounded by protoplasm (6) which sends amceboid processes out into the investing deuto- 
plasm. These nuclei with the investing layer of protoplasm are the ‘“‘ameeboid cells” of Ulianin. They 
afterwards increase by division, come to the surface of the yolk, and from thein is formed the blastoderm. 
2. Section through one of the cleavage spheres of the same. 6, amceboid cell, not yet transported to the surface. 
3. Section of egg at later stage. The ‘‘ameboid cells” (6) have migrated to the periphery of the egg, divided, 
and from them has been formed the blastoderm (0 7). 
4. Later stage, superficial view. The blastoderm has largely increased at the expense of the “ amceboid 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.” ep, epiblast. mes, 
mesoblast. , micropyle apparatus, arising as a patch of thickened epiblastic cells. 
Nore. — Ulianin homologizes the dorsal organ of Crustacea with the shell gland of Mollusca. 
7. Section through embryo after the appearance of the appendages. A, dorsal organ. The cells have become 
invaginated so as to formasac. dp, deutoplasm. ¢ yolk sphere. xc, nucleus of yolk sphere, with proto- 
plasmic investment. 
8-10. Gammarus pulex. From La Valette St. George, Studien iiber die Entwickelung der Amphipoden. 
Abhandl. naturforsch. Gesellsch. Halle, V., 1860. 
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 (Pl. VI.). , 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 shown 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 euticula remains 
attached to the epiblast until the atrophy of the dorsal organ. §, egg-membrane. a, larval skin. , dorsal 
organ. 
10. Portion of the upper half of the body. oc, eye. dp, remains of food-yolk. a, larval skin with the so-called 
micropyle (A) torn away from the sac of the dorsal organ (\’) which lies in fourth segment of the body. 
11-19. Development of Stomatoropa. Figures from Water Faxon, Cart Cravs, and W. K. 
Brooks. 
11. Youngest known stage of Stomatopod larva of the Hrichthus type of development (Krichthoidina), 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 (0 ¢ 7), a pair of stalked eyes (0c), two pairs of simple antennee (I, II), 
a pair of mandibles (III) without palpi, and two pairs of maxillz (IV, V). From the dorsal side of this 
head portion is developed a large shield or carapace 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 underlying 
segments back of the head. Behind the head is a region composed of eight segments, the five anterior of 
