DESCRIPTION OF FIGURES. 



Figs. 5, 6, 7, 8 (PL 1), and fig. 14 (PI. 2), have been redrawn in black 

 from drawings made in color from the preparations. The other figures as 

 they stand were drawn with the camera. Figs. 9, 10, 14 are semi-diagram- 

 matic in unimportant details. All but fig. 11 show the conditions in 

 Diaptomus. 



PLATE 1. 



Fig. 1. — An aesthetask (aes.) with its group of ganglion cells (». c). 

 The peripheral processes of the latter (n. f. per.) are shown entering the 

 aesthetask as a single strand. X 1040. Methylal method. 



Figs. 2, 3, 4. — Aesthetasks (aes.) and peripheral nerve fibrils (n. f. per.). 

 Fig. 2 shows the globule {gl.) which occurs pretty regularly. (Cf. fig. 5.) 

 All figures, X 1000; preparations by the methylal method. 



Fig. 5. — An aesthetask {aes.), drawn before the stain was fixed, showing 

 the nerve termination {ter.) on the wall of the sense organ. The globule 

 {gl.) near the base is characteristic. X 455. Methylene blue. 



Figs. 6, 7, 8. — Drawings giving the appearance of various groups of 

 nerve cells {n. c), with their peripheral (?!. f. per.) and central (n. f. en.) 

 fibrils. The depth of staining indicated is characteristic. All the figures, 

 X 1000; corrosive sublimate alcohol method. 



Fig. 9. — Abdomen of male, lateral, showing two nerve cells whose central 

 processes after uniting pass far forward. (Fii.) furcal ramus. X98; 

 methylene blue without fixation. 



Fig. 10. — Abdomen of female, lateral. The central fibre (n. f. cn.^ 

 could be traced as far forward as the second maxilliped. X 455; methylene 

 blue without fixation. 



fio] 



