ANATOMY OF THNIA MEDIOCANELLATA, 3 
the breadth and thickness of the individual segments as 
compared to their length, while leaving, however, the rela- 
tive measurement of our component zooid to the other 
intact. 
Taking as an example a colony 60 inches in length after 
alcoholic immersion, the following rough details were noted. 
—Head square shaped, tapering somewhat towards the neck, 
length ;%5 in., breadth 7%, in., thickness ;35 in. Neck 
(merely the narrowest portion of the colony from which the 
head expands upwards and the segments downwards) oval in 
outline, --4,in. broad by ;3, in. thick. In the first inch from 
the neck were about 100 segments, averaging +4, in. in length 
and =°; in. in breadth. In the second inch 60 segments. 
In the four succeeding inches 126 segments, the lowermost 
-!,’; in. broad, ;4, in. long, and ;3, in. thick. From 7th to 
10th inch, 121 segments. From 11th to 14th, 70. From 
15th to 18th, 64. From 19th to 22nd, 48. From 23rd to 
26th, 40. From 27th to 30th, 35; the lowermost segment 
being =2,°, in. broad, ;2, in. long, and +8, in. thick. From 
31st to 34th, 27. From 35th to 38th, 27. From 39th to 
42nd, 21. From 48rd to 46th, 20. From 47th to 50th, 15; 
at 48 inches from head, the segments being equal in length 
and breadth, -23, in. by 73, in. in thickness. From 51st to 
54th, 13. From 55th to 58th, 11. From 59th to 60th, 4; 
the last zooid being +17, in. broad, =3,3,in. long, and +3, in. 
thick. In all 800 segments. Hence, from the neck to the 
662nd segment, there is a gradual increase of the components 
of the colony in all dimensions, especially in breadth and 
thickness, and in a lesser ratio as regards the length; from 
the latter point the thickness of the segments continues some- 
what to augment, while the length greatly advances accom- 
panied by a corresponding decrease in breadth, until, at the 
765th segment, length and breadth are equal ; from the 765th 
to the terminal segment the thickness and breadth in 
especial gradually give way to advancing length; so that, 
viewing the colony either in front or laterally, there is a rapid 
tapering from the head to the neck, succeeded towards the 
centre by a progressive expansion which merges into a 
gradual decrease in body thickness towards the zooids ready 
to separate as completed lives from the parent stem. Look- 
ing at the components of the colony, towards the head half 
growth is expended in broadening the individual segments, 
towards the lower half lengthening out preponderates. At 
the 282nd segment the genital pit was apparent to the eye, 
and here an increase of breadth of segments rapidly ensued, 
from -*,!,th to -2,5;th of an inch. The genital pore was inva- 
