No. 4. — Cristatella : the Origin and Development of the Indi- 

 vidual in the Colony. By C. B. Davenport. 1 



Contents. 



Page 



I. Introduction 101 



II. Architecture of the Colony . 103 

 III. Origin of the Individual . . 106 



A. Observations. — Origin of 



1. The Bud .... 107 



2. The Alimentary Tract 111 



3. The Central Nervous 



System 113 



4. The Kamptoderm .115 



5. The Funiculus and 



Muscles .... 115 



6. The Body- wall . .117 



7. The Radial Partitions 119 



B. Comparative and Theo- 



retical Review of the 

 Observations on the 

 Origin of the Indi- 

 vidual 120 



1. Origin of the Polypide 121 



2. Interrelation of the 



Individuals in the 

 Colony 121 



3. Origin of the Layers 123 



4. Origin of the Alimen- 



tary Tract .... 127 



Page 



5. Origin of the Central 



Nervous System . 127 



6. Origin of the Funicu- 



lus and Muscles . 128 

 IV. Organogeny. — Development of 



1. The Ring Canal . . 120 



2. The Lophophore . . 130 



3. The Tentacles . . . 135 



4. The Lophophoric 



Nerves 136 



5. The Epistome . . .138 



6. The Alimentary Tract 139 



7. The Funiculus and 



Muscles .... 141 



8. Origin and Develop- 



ment of the Parieto- 

 vaginal Muscles . . 143 



9. Disintegration of the 



Neck of the Polyp- 

 ide 144 



10. Development of the 



Body-wall .... 144 



Summary 145 



Bibliography 148 



Explanation of Figures .... 152 



I. Introduction. 



At the suggestion of Dr. E. L. Mark, I began, in the spring of 

 1889, the study of fresh- water Bryozoa. While at the Laboratory of the 

 TJnited States Fish Commission, at Woods Holl, Mass., where, through 

 the kindness of Mr. A. Agassiz, I had the opportunity of spending the 



1 Contributions from the Zoological Laboratory of the Museum of Comparative 

 Zoology, under the direction of E. L. Mark, No. XIX. 

 VOL. xx. — no. 4. 



