HABITS, ETC., OF CEREBRATULUS LAOTEUS. 97 



The Habits and Early Development of Cere- 

 bratulus Lacteus (Verrill). 

 A Contribution to Physiological Morphology. 



By 



Clias. B. Wilson. 



With Plates 9—11. 



Outline. 



I. Inteodijction . . . . . . .99 



II. The Adult Worm. 



A. Determination of Species .... 102 



B. Habitat and Habits : 



(1) Geographical distribution .... 103 



(2) Burrows and burrowing .... 104 



(3) Food 107 



(4) Breathing . . . . . .109 



(5) Locomotion . . . , . .110 



(6) Dismemberment ..... 112 



(7) Regeneration ...... 119 



III. Larval Development. 



A. Sexual Organs: 



(1) The ovaries : 



(a) Germ tissue ..... 121 



(b) Oogenesis ..... 123 



(c) Formation of oviduct .... 125 



(2) The testes : 



(a) Sperm tissue ..... 126 



{b) Spermatogenesis .... 126 



(c) Formation of sperm-duct . . . 127 



B. Egg-laying ...... 128 



c. Fertilisation and Ripening : 



(1) Fertilisation . . . . . .130 



(2) Formation of polar bodies .... 131 



(3) Activities of polar bodies : 



(a) Description of activities . . . 133 



(b) Connection with egg .... 135 



(c) Polarisation ..... 135 

 VOL. 43, PART 1 . — NEW SERIES. G 



