The Development of Cordylophora^ 



Chandler Fulton 



Department of Biolop.ij, Brandeis University, Waltham 54, Massachusetts 



One of the challenging problems of development is the manner 

 in which a multi-cellular organism acquires and regulates its shape, 

 pattern, or proportion. Colonial hydroids offer especially favorable 

 material for study of this problem because their colonies are com- 

 posed of a repeating pattern of hydranths arranged on tubular 

 stems and stolons ( Fig. 1 ) . Hydroid colonies grow asexually by the 

 elaboration of stolons attached to a substratum; at regular intervals 

 the stolons send up uprights which bear hydranths, grow, and 

 branch. The primary concern of this paper is the manner in which 

 colonies develop this regular, repeating pattern. 



I chose to work with the brackish-water hydroid, Cordijlophoia 

 lacustris, because it is exceptionally hardy and has a simple colony 

 pattern. For study of the development of colonies, it is advantageous 

 to have a refined and reproducible method of laboratory cultiva- 

 tion similar to that de\eloped by Loomis for Hydra Uttoralis. One 

 can grow Cordijlophoia colonies on glass microscope slides slanted 

 in beakers of culture solution, with no flow of water or other spe- 

 cial treatment ( 1 ) . The defined culture solution contains ionic so- 

 dium, potassium, calcium, magnesium, chloride, and bicarbonate. 

 All of these ions, with the exception of bicarbonate, are essential 

 for growth at a maximum rate, and the proportion of the ions is 

 critical. The cultures are fed Artemia larvae once daily, and the cul- 

 ture solution changed after feeding and again later in the day. Be- 

 tween feedings, the beakers are kept in the dark at 22 , though 



lA much abridged form of the paper presented at the meeting. Relevant Hterature 

 citations and supporting data will be presented in papers to be published elsewhere, 

 and may be found in reference ( 2 ) . 



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