Am.  jour.  Pbarm. )  Current  Literature.  41 
January,  191o.    J  ~ 
and  is  used  in  the  construction  of  house  walls  (large,  thick  blocks) 
or  house  roofs  (large,  thin  slabs).  When  exposed  to  the  air,  this 
soft  quarried  rock  hardens  into  a  form  of  limestone,  much  like 
concrete  in  appearance.  As  in  all  limestone  formations  of  any 
considerable  thickness,  caverns  and  underground  tunnels  are  worn 
into  the  softer  strata  by  the  action  of  rain  and  underground  water. 
Several  caverns  of  this  character  are  visited  by  tourists  in  Bermuda, 
and  some  of  them  have  pools  of  salt  water  replenished  by  under- 
ground supplies  from  the  ocean.  There  are  limestone  sinks,  which 
represent  caves,  the  roofs  of  which  have  fallen  in.  A  number  of 
these  sinks  are  dry,  others  are  filled  with  water.  One  of  the  most 
frequently  visited  of  these  depressions,  filled  with  salt  water,  which 
comes  underground  from  the  ocean,  is  Devil's  Hole,  in  which  are 
.kept  a  number  of  the  characteristic  fishes  of  the  Bermuda  archi- 
pelago, such  as  the  grouper,  the  angel-fish,  the  red-snapper,  and 
others  equally  celebrated.  The  walls  of  the  Devil's  Hole  are  rather 
steep,  and  in  places  overhanging,  so  that  the  fresh  water  from  the 
rocks  above  drips  into  the  pool  beneath.  Here  were  found  stalac- 
tites from  an  inch  to  two  inches  in  length  and  coated  with  a  covering 
of  blue-green  algae. 
Several  of  these  stalactites  were  broken  off  from  the  overhanging 
wall  in  Devil's  Hole,  June,  1905,  and  kept  dry  for  subsequent  study, 
but  the  material  was  overlooked  until  the  present  summer  (1914), 
when  a  study  was  made  of  it.  Small  pieces  of  stalactite  were  crushed 
in  water  and  examined  under  the  microscope.  The  blue-green  algae, 
which  alone  were  present,  were  identified  with  Josephine  Tilden's  2 
first  volume  of  "  Minnesota  Algae."  The  algae  found  on  this  examina- 
tion consisted  of  Chrootheca  Richteriana  Hansg.,  Gleocapsa  aerugi- 
nosa (Carmichael)  Kuetzing,  and  G.  gelatinosa  Kuetzing,  G.  quart  er- 
nata  (Brebisson)  Kuetzing,  and  Gleotheca  linearis  Naegeli.  At- 
tached to  a  small  red  alga  (not  identifiable)  which  was  fastened  to 
a  piece  of  stalactite  was  found  Microcystis  Hos-aqua  (Wittrock) 
Kirchner.  The  most  abundant  blue-green  alga  was  Chrootheca  Rich- 
teriana Hansg.,  which,  according  to  Josephine  Tilden,  consists  of  a 
somewhat  gelatinous  plant  mass,  thick  or  more  or  less  expanded,  of 
a  blue-green  or  yellowish  color.  The  cells  found  in  these  masses  are 
18  to  24  microns  in  diameter,  once  to  twice  as  long  as  wide,  single 
2  Tilden,  Josephine,  "  Minnesota  Algae,"  vol.  i :  "  The  Myxophycese  of 
North  America  and  Adjacent  Regions,  including  Central  America,  Greenland, 
Bermuda,  the  West  Indies,  and  Hawaii/'  Bot.  Ser.  viii,  1910. 
