6 Miss D. J. Lloyd. Influence of Osmotic 



Table I. 



Composition of water. 



Density. 



Salinity. 



Osmotic pressure 



(atmospheres) 

 (approx. within 

 0"5 atmosphere). 



Length of life 



of Gr, lllvcP, 



in the solution. 









grin. 













per litre. 







1. 



Distilled water . . 



1 -ooo 



-oo 



— 



1-18 hours. 



2. 



Tap water 



1 -ooo 



o-oo 



— 



6 hours-3 days. 



3. 



100 c.c. distilled water — 











+ 5 c.c. sea-water 



1 -ooo 



1-60 



1 -o 



3-6 days. 



4. 



+ 10 „ 



1 -ooi 



3-11 



2-0 



Indefinitely. 



5. 



+ 20 ,, „ 



1 "002 



5 -70 



3-5 





6. 



+ 50 „ 



1 -007 



11 -4 



7-5 





7. 



+ 100 „ „ 



1 -012 



17 -1 



11 -o 





8. 



+ 200 „ „ 



1-015 



22 -8 



15 -0 





9. 



+ 500 „ 





28 -5 



18 -5 





10. 



Sea-water 



1 -023 



34 2 



22 -5 





11. 



100 c.c. sea-water — 













+ 10 c.c. 2-5M NaCl 



1 -030 



44 "3 



29 -5 





12. 



+ 20 „ • „ 



1 -037 



52 -8 



33 -5 



14 days- 













Indefinitely. 



13. 



+ 30 „ 



1 -043 



60-1 



40-5 



18-40 days. 



14. 



+ 40 „ „ 



1 046 



66 -7 





5-20 „ 



15. 



+ 80 „ „ 



1 -058 



83 -8 





3-7 „ 



16. 



+ 200 „ „ 



1 -073 



109 -0 





6 hours-1 day. 



The solutions used were made by mixing known volumes of sea-water with 

 distilled water, or with 2 - 5M Nad, calculating the salt content, and from 

 this taking the osmotic pressure from the values given in Kriimmel's 

 ' Handbuch der Ozeanographie ' (8). 



The salinity of the sea-water used was measured by titrating against 

 standard silver nitrate and determining the chlorine value. Knudsen's 

 tables (7) give the formula for converting the chlorine value obtained into the 

 salinity value. 



It will be seen that the worms are capable of living for an indefinite time 

 in water which has an osmotic pressure of more than 2 and less than 

 33 atmospheres. Between these limits the worms remain perfectly normal 

 in appearance. In solutions more dilute and in fresh and distilled water the 

 worms swell up to four or five times their normal size. In water having a 

 salinity of 66 per cent, or more they become shrivelled. 



IV. Normal Eegenekation of the Posterior End. 



The changes which set in in G. ulvce after section and which culminate in 

 the restoration of the lost parts and production of a complete worm fall 

 under the head of regulatory rather than of regenerative changes. There 

 is no growth in the ordinary sense of the word, since the first product of 



i 



