Phylum XVII 



Chordata, Class Ascidiacea 



NOTES ON THE CULTURE OF EIGHT SPECIES OF 



ASCIDIANS 



Caswell Grave, Washington University 



AMMAROUCIUM CONSTELLATUM 



THIS ascidian is viviparous. Free-swimming larvae may be secured 

 in abundance at Woods Hole during the months of July, August, 

 and September by placing large colonies of this ascidian in glass aquaria 

 before a window in the laboratory. The best results have been obtained 

 when colonies were collected the day before tadpoles were desired and 

 kept in running seawater during the night. Care should be taken that 

 the colonies are uninjured and are not placed in containers with other 

 material, otherwise the sexually mature zooids are likely to die and be 

 extruded on the surface of the gelatinous mass. Tadpoles are set free 

 from the colonies in swarms at and just after sunrise, hence the aquaria 

 containing the colonies should be transferred to a window table at dawn. 

 Larvae escape from the colonies at other times in the day one by one. 

 When liberated, the tadpoles swim immediately to the surface of the 

 water and collect at the most illuminated edge of the container where 

 they may be captured easily with a pipette. 



Immature tadpoles and various earlier developmental stages may be 

 secured by squeezing a colony in the hand over a culture dish of sea- 

 water. With the mass of ascidiozooids, tadpoles, embryos, and eggs thus 

 forced from the gelatinous matrix a considerable quantity of debris is 

 included, giving the water a milky appearance. This settles slowly and 

 may be removed by decantation, two or more changes of water being re- 

 quired. Mature tadpoles may be had in small numbers in this way 

 also. For a few seconds after having been squeezed from the colony 

 they lie motionless on the bottom of the dish, but soon swim about, 

 apparently being stimulated to activity by light or by contact with pure 

 seawater. (Grave, 192 1.) 



SYMPLEGMA VIRIDE, POLYANDROCARPA TINCTA, AND P. GRAVEI 



Wild colonies of these ascidians almost without exception are found 

 encrusting the under side of dead coral rock, empty shells of mollusks, 



560 



