UTERINE SPINDLE OF PLANOCERA INQUILINA. 275 



number of worms found in a single whelk, although we have 

 secured as many as eight from one specimen. After removing 

 the shell, the branchial chamber of Sycotypus is slit open and the 

 worms removed to dishes of fresh sea water. This operation 

 was done very shortly after the animals were brought into the 

 laboratory. 



When the eggs are fully matured the polyclad lays within 

 several hours after being transferred; otherwise twelve or even 

 twenty-four hours may elapse before eggs are deposited. Usually 

 the eggs are laid in a helicoid spiral on the bottom or sides of 

 the dish, as Wheeler ('94) and Surface ('07) have observed; but 

 quite often oviposition occurs beneath the surface film of the 

 water, in which case the egg string takes the form of a slightly 

 curved ribbon. In the latter instance the worm lies with its 

 ventral surface upward, in which position one can readily study 

 the entire process under the binocular. The eggs are forced out 

 by rhythmic contractions of the egg ducts, and at the same time 

 embedded in a perfectly transparent gelatinous substance of a 

 very sticky consistency. The average time for the act of ovi- 

 position is about 15 minutes. Each egg is provided with a 

 delicate capsule, probably secreted by the shell gland surrounding 

 the egg duct. Occasionally a single capsule incloses two eggs. 

 A string may contain as many as 2,000 eggs. Adult worms were 

 obtained showing eggs in every stage of development from the 

 beginning of the growth period up to the time of laying. Eggs 

 were killed just at time of oviposition and at fifteen minute 

 intervals for several hours afterward. In this way a complete 

 series of stages covering the entire period of growth and matura- 

 tion was obtained. 



Adults and eggs were killed in the bi-chloride-acetic-formalin 

 mixture described by Bartelmez ('12). 



SOLUTION i. 



Saturated solution of .7 per cent. NaCl 94 c.c. 



Glacial acetic acid 6 c.c. 



SOLUTION 2. 

 Neutral formalin (commercial formaldehyde neutralized 



with MgCOs) 10 c.c. 



The two solutions were kept separate until the time of using. 



