MUSEUM OF COMPARATIVE ZOOLOGY, 245 
nections between the cavities of the hydrothece and those of the stem and also 
between the different stems through their lateral communications, while others 
were carefully cleaned of their contents and stained with eosine, and of still 
others numerous cross-sections were also made, I arrived at the following results, 
The basal portion of the main stem and of most of the branches are polysipho- 
nic, and these cauline tubes decrease in number towards the distal extremities 
until they are but two, then one, and finally they are all discontinued ; where 
two exist, they are found to occupy opposite sides of the branch, one on the 
upper and one on the lower surface, the hydrothece imbedded in and stretch- 
ing out from the sides of the branches; where one only is left, it usually occu- 
pies the upper surface of the branch. These cauline tubes are provided with 
a number of perforations, regularly arranged, by means of which they have 
direct communication with the contents of each hydrotheca. Where but one 
tube exists, the perforations may readily be seen in the floor of the tube or 
stem, one near the base of each hydrotheca and towards the opposite side of 
the stem from which the hydrotheca near whose base it lies is imbedded ; 
they are therefore arranged alternately on opposite sides of the tube. See 
Plate IIT. Figs. 16, 20. 
Where there are two tubes of the stem, an upper and a lower, there is an 
orifice in the lower tube directly opposite each one in the upper tube, and 
through these apertures there extend processes of the ccenosare which com- 
municate with each other and with the neighboring hydrotheco. By this 
means direct and abundant communication is established between all portions 
of the cauline stems and the hydrotheos. By the aid of the cross-sections I 
find that the walls of the cauline stems, where there are two of them, never 
adjoin one another, while the walls of the opposite hydrotheca do touch 
throughout. See Plate IIL, Figs. 17 5, c, d. 
Thus far the structure described does not disagree with anything given in 
Professor Allman's description, but careful camera-lucida sketehes of front 
views of portions of the extremities of the branches where the cauline tubes 
are discontinued do not indicate any floor to the hydrothecæ, but show them 
to be fuliy open below without a floor. Still more distinet!y and conclusively is 
this shown in a camera-lucida drawing of a lateral view. See Plate III, Fig. 18. 
Figs. 19 and 20 on Plate III. are from the type specimens, showing the 
same structure, In Fig. 19, Plate IIL, the uppermost hydrotheca belongs to 
the right side of the branch, the median and lower ones to the left side. In 
Fig. 18, Plate III., the hydrothece of one side only are represented. 
Sertularia complexa sp. nov. 
Plate IV. Figs. 26-28 b. 
Trophosome, — Hydrocaulus attaining a height of about three quarters of an 
inch, unbranched, divided by transverse nodes into rather short internodes j 
hydrotheco not springing from opposite sides, but imbedded in one side of the 
stem, deep, the lower halves of each pair resting against each other, the distal 
