THE MALAYAN SPECIES OF ONYCHOPHORA. 87 



Fig. 20 a. — Tliis figure shows an oblique section which passes through 

 the posterior end of the anal groove (an.ffr.), and on the left cuts the 

 rudiment of the last appendage along its whole length. Note the last 

 somite (m. a. a., som."). 



Fig. 20 b. — This figure shows a section in a similar direction and parallel 

 to the one illustrated in Fig. 20 a. Note the duct of the male accessory 

 gland (m. a. g.) and the renal organ {ren. or.), derived from the last 

 and penultimate somites respectively. 



Figs. 21a and 21^ (x 120). — These figures represent sections of a male 

 embryo of the same age as the one illustrated in Fig. 6 on Plate 5. 



Fig. 21 a. — This figure shows a section of the male accessory gland 

 {m. a. g.) and of the last ventral organ {vcn. o.), which is vestigial in 

 character. 

 Fig. 21 i. — This figure shows a section of the last renal organ {ren. or.), 

 the male accessory gland {m. a. g.), and the last fully developed 

 ventral organ {ven. o.). 



PLATE 9. 



Figs. 22a, 22b, and 22c (X 50). — These figures represent the thirty- 

 second, the fifty-ninth, and the eighty-first sections respectively of a transverse 

 series of the brain of an embryo which was slightly older than the one shown 

 in Fig. 5, but younger than that illustrated in Fig. G on Plate 5. 



Fig. 22 a. — This figure shows a section passing through the archicerebral 

 (a. lo.) and the first (/o.') or antennal lobe of the brain, as well as the 

 first pair of ventral organs {v. o.') near their posterior limit. On the 

 right side the eye is shown ; but on the left the section passes in front of 

 that organ. On the ventral aspect the lips situated on either side of 

 the mouth, with the tongue passing down between them, are repre- 

 sented. 

 Fig. 22 b. — This figure shows a section passing through the archicerebral 

 {a. lo.) and the third (/o.^) lobe of the brain ; the second (v. o.^) and the 

 divided third (v. o.^" and v. o.^*) ventral organs. On the right side it 

 passes along the anterior border of the para-cesophageal cord ; on the 

 left it passes in front of that cord. 

 Fig. 22 c — This figure shows a section passing through the third (/o.') 

 and fourth {lo.^) lobes of the brain, as well as the fourth ventral organ 

 (p. 0.^), which corresponds to the anterior pair of walking appendages. 

 On the right side it passes behind the para-cesophageal cords ; on the 

 left the para-cesophageal cord is cut along its whole length. Note 

 that on the left side the fourth lobe f/o.'') of the brain, which lies on 

 the dorsal half of the para-cesophageal cord, is pierced by the fibres of 

 the mandibular nerve. 



