1878. ] Discolored Waters of the Gulf of California. 87 
Mr. Darwin in his “ Naturalists Voyage Around the World,” 
encountered a patch of similarly discolored water off the coast of 
Peru. According to his account, the water when examined by 
the microscope was “seen to swarm with minute animalcule dart- 
ing about and often exploding. Their shape is oval and con- 
tracted in the middle by a ring of vibrating curved cilia. It was, 
however, very difficult to examine them with care, for almost the 
instant motion ceased, even while crossing the field of vision, 
their bodies burst.” From the foregoing it is evident that the 
water of the two localities is discolored alike by the same cause. 
Those from the Gulf of California exhibited the same rapid 
to and fro motion as the ones seen by Darwin, and this 
motion was succeeded by a rotatory movement on the longer 
axis. Sometimes the rupture took place as soon as the latter 
motion ceased, and at other times the animal was motionless fora 
few moments preceding its final dissolution; and it was during 
these intervals of quiescence, only now and then observed, that 
anything like a correct impression of its general outline and 
structure could be gained. The following is the result of numer- 
ous observations extending over considerable time. The animal 
is oval in outline, with a projecting lip at its broad extremity, 
fringed with cilia. The rotatory movement took place around the 
smaller end as a pivot, and it advanced the same end in its to and 
fro movements. The envelope is a transparent and, apparently, 
structureless membrane, and in its interior are greenish-yellow 
granules, or bodies with dark rims and bright centres. These 
= bodies floated loosely in the cavity of the animal, for when it 
revolved they changed their places like pebbles in a revolving 
_ cask. They averaged about the 1-12000 of an inch in diameter. 
_ According to Mr. Darwin the bursting, which generally oc- 
a curred at the extremities of the body, is due to an expansion of the 
 tegumentary covering. I can not reconcile this with the results of 
_ my own observations. On the contrary, I noticed a contraction 
-= to take place in the transverse axis of the body; its length was 
_ increased and its transverse diameter diminished; in other words, 
-the oval form was replaced by an oblong. This will better illus- 
_ trate why the rupture generally took place at one of the extremi- 
ties of the body. If these observations are correct the bursting 
of the envelope would be the result of an active rather than a 
passive action. The only reasonable way of accounting for an- 
; . : 
VOL, XII.—No. II. 
Teu a a Oe SEE eRe RE, n u a a a ee Meee Re Sk ae mena. R aA A ita a a a a a AA 
