DEVELOPMENT AND ANATOMY OF SOME EARTHWORMS. 31 
EXPLANATION OF PLATES 2—5, 
Illustrating Professor A. G. Bourne’s paper “On Certain 
Points in the Development and Anatomy of some Earth- 
worms.” 
PLATE 2. 
Fies. 1—8.—From Mahbenus imperatrix, fully described in the text. 
Fig. 1. W, m. Primary “ mesoblasts.” Zp. Epidermis. al. ep. Alimentary 
epithelium (the cells fully shown here and in Fig. 8, partially so only 
in Figs. 2—7). Muse. Cells which give rise to the muscle of the 
body-wall (their presence here at this stage will be discussed in a 
subsequent paper). «. marks a corresponding spot in Figs. 1—3. 
Fig. 2, M. Row of cells growing from the primary “ mesoblast.” Other 
letters as before. 
Fig. 3. Letters as before. 
‘Fig. 4. n. Neuroblast. . Cells forming nerve-cord. Sept. Septum. 
Cel. ep. Celomic epithelium. The line A B in this and Figs. 5 
and 6 marks a corresponding level. Other letters as before. 
Fig. 5. a, 4, c. Row of cells giving rise to primary setal matrices, as 
s., 8. Neph. Nephridial matrix. 
Fig. 6. s. Continuation backwards of the row a, 4, c, of the preceding 
figure. Neph. Nephridial matrices; the actual nephroblast does not 
come into this section. 
Fig. 7. Letters as before. 
Fig. 8. Letters as before. 
PLATE 3. 
Fics. 9—15.—Moniligaster (probably M. sapphirinaoides). 
Fig. 9. Portion of an embryo flattened out. Neph. Young nephridia. 
a. Portion of the nerve-cord. Sept. Septa. yp. m. Primary setal 
matrices. 7. m. Secondary setal matrices in process of formation. 
S. m. 4. and §. m. o. Inner and outer secondary setal matrix. Sed. 
Rudiment of a seta. wz. Series of large cells of unknown significance. 
Figs. 10—13, Transverse sections, described in the text. p.m. Primary 
setal matrix. §. m.7. and §. m.o. Inner and outer secondary setal 
matrix. NVeph. Nephridium. Zp. Epidermis. 2. Epidermic ingrowth. 
Fig. 14. Surface view of an advanced secondary setal matrix. se¢., set. 
The two séte of a couple. 
Fig. 15. Similar structure from a longitudinal section. 
