C. L. Edwards 293 
SVMMARY— {continued). 
flovidana Pourtal^s 
H. atra Jager 
Body-wall 
Firm ; mean thickness, 4 mm. in adult and 
1-5 mm. in young. More variable in the adult 
but, in general, " thick skinned." 
Flaccid ; mean tliickness 1'6 
mm. in both adult and young. 
In general, "thin skinned." 
Rosettes 
Stellate, central rod short, branches swollen at 
ends. Growth-stages of the perforated plates. 
Central rod somewhat elon- 
gated, branches more nearly 
at riglit angles. Longer and 
more delicate. 
Perforated plates 
and rosettes 
with holes 
(1) Developmental stages; Type a, 4 holes; 
Type h, 8 holes. 
(2) Develoi)ed plates ; mean number of holes, 
13 in bivium ; 15 in trivium. With age, holes 
fill n\) with lime. 
Of the statistical series of 300 
rosettes and rosettes with 
holes, 2 had 3 holes, 4 had 
2 holes and 19 had 1 hole. 
Rare variates may have moi'e 
holes (up to 6) but such per- 
forated plates are not like the 
developed perforated plates 
of JI. Jioridaaa. 
Occasional elongated " But- 
tons" occur with 2 jifi-irs of 
central holes and 1 distal 
hole at each end. 
Average number 
of peripheral 
holes in discs 
of tables 
5-2 
3-7. 
Number of ro- 
settes and per- 
forated plates 
per sq. cm. 
5,000,000 to 12,000,000 
50,000. 
Pedicels and pa- 
pillae in biv- 
ium 
Large majority cylindrical and with suckers are 
pedicels. 1 out of 16, papillae. 
Majority conical and without 
suckers are papillae. 
Types of end- 
plates 
In bivium, A (47 7„), B (41 C (9° /J, and 
D ( 17„)- 
In trivium, A (92%), B {6°/J and C(27J. 
Mean diameters of all types larger than in 
ff. utra. 
In bivium, A {-^'l^), B{WI ), 
C (34 7J, D (ir/J and E 
(47o)- 
In trivium, A (72 7 J, B (19 7 J, 
C(67J, i>(2 7„) andAX27J. 
Only 1 in iDivium large 
enough to be placed in Type 
A. 
Polian vesicles 
Simple, or branched ; solitary, or in tufts ; mean 
number, in adult, 13, with range of 1 — 92. 
74% of young with 1 vesicle. Branching and 
formation of tufts dvie to growth. 
Simple ; mean number ; in 
adult, 21, with I'ange of 1 — 
56 ; in young, 10, with range 
of 4—24. 
Stone-canals 
Mean total num- 
ber in adult 
Mean average 
length in adult 
37, with range of 1—149. 
54°/^ more than H. atra. 
5 mm. 
24, with range of 15 — 70. 
7 mm. 40% longer than in 
H. floridana. 
