200 CHORDATA. 



living embryos in all stages of development can be found. 

 Fresh specimens kept in a large jar of sea-water during the 

 summer will discharge larvae. These swim rapidly, and usually 

 swim away from the light. Does this correspond with Botryl- 

 lus? Is this negative phototrophism adaptive? 



The tailed larvae may be picked up with a pipet while swim- 

 ming, dropped into fixing fluid, and finally stained and mounted. 

 Others may be transferred to watch-glasses and studied. If 

 the larvae are kept in watch-glasses of sea-water for some hours 

 some will attach. The dishes may then be kept in a cage under 

 a wharf submerged in sea-water, or in a dish where pure sea- 

 water can be conducted to it. Under these conditions they 

 will develop readily, but they must be kept clean from sediment 

 by washing them with a gentle current at least twice a day. 



In larvae that have been previously stained and mounted 

 observe: 



(a) The shape of the animal and its division into body and 

 tail. 



(6) The thick test, and the oral and atrial openings. 



(c) The adhesive organs. How many are there? 



(d) The notochord. How far does it extend? 



(e) The tail muscles. 



(f) The pharynx, with as yet few gill clefts, the endostyk, 

 esophagus, stomach, intestine, and yolk-mass. 



(g) The cerebral vesicle with the eye-spot and otolith. 



If young individuals that have been attached but a short 

 time, but have lost their tails, are stained and mounted, they 

 will be found very instructive when compared with the larva. 

 The complete degeneration of the tail and the final rotation 

 into the position of the adult can be traced in a series of indi- 

 viduals. 



Drawings of an adult individual, of a larva, and of a young 

 individual are desirable. 



Van Name: Compound Ascidians of the Coasts of New England and Neigh- 

 boring Provinces. Proc. Bost. Soc. Nat. Hist., 34, 1910. 



