564 Phylum Chordata 



MOLGULA CITRINA 



In Molgula citrina fertilization and development of the egg take place 

 within the atrial chamber of the parent. Eggs and embryos in various 

 stages of development may usually be found together in the atrial 

 chamber of sexually mature individuals from June 15 to September 15 

 at Woods Hole, Mass. Egg production and development are not af- 

 fected by the transfer of sexually mature individuals from their natural 

 habitat to aquaria in the laboratory. One lot of about 30 adults con- 

 tinued to liberate large numbers of active larvae daily from June 22 

 until discarded July 27. 1926. Adult individuals may usually be taken 

 in considerable numbers with scrapings from piles. These, if separated 

 from the associated debris and placed in aquaria of running water, 

 readily and invariably re-attach themselves to the bottom or side of the 

 container. 



When larvae are desired, the aquarium containing the sexually mature 

 adults is transferred to a table before a window. Under laboratory con- 

 ditions, larvae are set free with the same frequency at one time of the 

 day as another. As larvae escape from the atriopore, they may be easily 

 seen as they swim to the surface where they may be taken with a pipette. 

 This larvae lacks a light-sensitive sense organ and does not orient to 

 light, but it has a statolith and orients negatively to gravity when first 

 liberated by the parent. (Grave, 1926.) 



Bibliography 



Grave, Caswell. 1921. Ammaroucium constellatum (Verrill). II, The structure 



and organization of the tadpole larva. J. Morph. 36:71. 

 1926. Molgula citrina: activities and structure of the free-swimming larva. 



J. Morph. and Physiol. 42:453. 



1932. The Botryllus type of Ascidian Larva. Papers from the Tortugas 



Laboratory, vol. 28. (Reprinted from the Carnegie Inst, of Wash. Publ. No. 435.) 

 1935. Metamorphosis of Ascidian larvae. Carnegie Publ. No. 452. Pa- 



per IX. 



, and Woodbridge, Helen. 1924. Botryllus schlosseri. 39: Ibid. 39. 



CULTURE METHODS FOR ASCIDIANS 



N. J. Berrill, McGill University 



METHODS OF CAPTURE 



ASCIDIANS are sessile, marine organisms varying considerably in 

 i habitat. Many forms are littoral, to be found in greatest quantity 

 immediately above or below the low water spring tide level. Others may 

 be found attached to the under surface of floating objects, while many 

 forms are found only in deeper water attached to rocky or hard surfaces, 

 or embedded in sand or mud without any strong attachment. In general 



