262 HUGH WATSON. 



Fig. 64. — x 22. A. gibbonsi rubella; side view of part of pedal 

 gland. 



Fig. 65. — x 119. A. gib])onsi rubella ; transverse section through 

 fold in terminal vesicle of pedal gland. 



Fig. 66. — ^x 114. A. diuiidia; transverse section through fold in 

 terminal vesicle of pedal gland. 



Fig. 67. — X 25. A. gibbonsi rubella; ventral grouj) of nerve 

 ganglia. 



Fig. 68. — x 60. A. dimidia; section through pedal ganglia and 

 pedal commissure, cut slightly obliquely, and showing pleural ganglion 

 on the right and cerebro-pedal connective on the left. 



Fig. 69. — x 120. A. dimidia ; sections of nerve-cells in right 

 parietal ganglion. 



PLATE XY. 



Fig. 70. — X 16. Apera gibbonsi rubella; cerebral and buccal 

 ganglia. 



Fig. 71. — x 32. A. dimidia; cerebral and buccal ganglia. 



Fig. 72. — x 25. A.sexangula; cerebral and buccal ganglia. 



Fig. 73. — x 30. A. dimidia; left half of ventral group of ganglia. 



Fig. 74. — x 33. A. sexangula: right half of ventral group of 

 ganglia. 



Fig. 75. — x 6. A. dimidia; semi-diagrammatic figure showing the 

 distribution of the nerves from the ventral group of ganglia. 



Fig. 76. — X 5. A. sexangula; tentacular retractors of an ab- 

 normal specimen. 



Fig. 77. — X 26. A. gibbonsi rubella; transver.se section through 

 niovith. 



Fig. 78. — x 15. A. gibbonsi rubella; transverse section through 

 crop and salivary glands. 



Fig. 79. — x 100. A. gibbonsi rubella ; transverse section through 

 wall of crop. 



PLATE XVI. 



Fig. 80. — X 50. Apera dimidia; transverse section through re- 

 tracted upper tentacle in front of eye. 



Fig. 81. — X 50. A. dimidia; transverse section through retracted 

 upper tentacle, showing anterior part of eye. 



