ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
25 
as the area we have been considering is, it is apparent that, while some 
forms are common to all, certain restraining influences check the spread 
of others, so that they become more or less characteristic of the several 
regions. Moreover, the mixed nature of the fauna shows that we have 
to do with several sources of origin, some of which date back to geo- 
logical periods marked by a different arrangement of the land, and a 
consequent change in the temperature of the water.” 
Biological Examination of Lake Michigan.* — Dr. H. B. Ward 
edits a bulletin on this subject, describing the lake with its fauna and 
flora, and with speciaPreference to the plankton. His general conclusions 
in regard to the plankton are the following: — The plankton is the 
source of food supply ttf all lake fish ; its rapid reproduction affords a 
constant supply in spite of continued destruction. The amount of 
plankton in Lake Michigan in tho (Transverse Bay) region examined is 
limited. The enormous area compensates for this limited amount. The 
plankton is uniformly distributed horizontally. In summer it is accu- 
mulated near the surface, and very little occurs below 25 metres, 
except near the bottom. The uniform horizontal distribution of the 
plankton indicates that the plankton-eating fish find food in limited 
quantities everywhere. The bottom flora and fauna are not enough to 
support large numbers of bottom-feeding fish within circumscribed areas. 
The well-known migrations of whitefish schools along shore seem thus 
to be correlated with the non-localised food supply. There is a plentiful 
supply of whitefish food on the old fishing-grounds. No reason can be 
assigned for the diminution in numbers except overcatching. By intro- 
ducing suitable vegetation, the fish-producing powers of the lake might 
be vastly increased. Dive appendices contain brief accounts of the 
aquatic plants, by H. D. Thompson ; Protozoa, by C. A. Kofoid ; 
Rotifera, by H. S. Jennings ; Turbellaria, by W. M £ M. Woodworth ; 
and Mollusca, by Bryant Walker. 
Poisoning of Freshwater Animals by Hypochlorite of Lime.f — 
Prof. R. Dubois has investigated this not uncommon event. Trout are 
particularly susceptible, being readily asphyxiated. Other fishes resist 
longer, but eventually succumb. Crayfish and other freshwater animals 
also perish. Trout killed by hypochlorite of lime are readily recognised 
by their discoloration, &c., and should never be bought. Not that 
they are injurious, but the practice of thus poisoning them is quite fatal 
to the stream. 
Tunicata. 
Distribution of Doliolum.J — Dr. ^ • Borgert has worked over the 
specimens of Doliolum collected on the ‘Yettor Pisani’ expedition. 
No new species were found, but the recording of D. tritonis and D. 
nationalis in the Pacific is new. The number of species found in the 
Atlantic Ocean is the same as that from the Pacific, but the actual 
species are not quite the same. Thus D. 7-arum Grobben is not known 
from the Pacific, nor D. ajfline Herdman from the Atlantic. 
* Bull. Michigan Fish Comm., No. 6 (1896) 100 pp. and 5 pis. 
t Ann. Soc. Linn. Lyon, xlii. (1895) pp. 49-52. 
t Zool. Jahrb. (Abtli. Syst.), ix. (1896) pp. 714-9. 
