47 
liir-r° nnt * t0 ba com P osed of liglit and dark lin#», formed by 
, Ul f numbers of irregular cellular bodies arranged longi- 
fro i " lall y in various degrees of aggregation. When separated 
f 0r ,“ eac b other, these cellules present one general lengthened 
H n 'i tern| inatiug at either end in a point, at the base of 
i ,c » is a 
Vote 
rim, resembling the neck and pointed stopper of a 
n UM nier ‘ ® ctween the two extremities, the body is straight, 
- ls minute globular cells arranged sometimes in pairs, at 
Cr s irregularly, and occasionally in rings round it. If 
into* 6 ^ *° un dcrgo still further decomposition, these separate 
Jude 8lna ^ er bodies of the shape of a Florence flask, which 
Ce ^ s » w bh'h form the ultimate component parts of the 
l )||| ^ r still further decomposition, separate into minute glo- 
^efo‘ e crusl - Their union is of the most intimate kind, and 
p 0 j re decomposition has begun, it is impossible to deleet the 
C 0 f ?..°f union between them. Ellis, in his “Essay” on 
tb e juries, has given a figure of a perfectly organized cell of 
Q j, ■ Ptacomus, which differs hut slightly from those of the 
ij. Qrrucosa ; but most probably they difl’er in every species. 
V / e Pul^pidorn of the Hydroida, we have seen is external, 
■ Her 
a Bew an( ^ remarkable change has taken place, and it 
ati(| “ ec °«ie the internal solid skeleton which gives form 
8|| a °Usis(ence to the whole. It is covered from the root to 
Pe*j Q ,® branches with an investing membrane, similar to the 
c Hn a n euni of hones. This membrane, which is lihrous, is not 
Vi * demonstrable at all seasons of the year, or in all 
Vo n eDS ‘ Though this appears to be independent of 

# Pti‘ S ’i ^ have found it more clearly apparent about 
“te r er ’ Qntuber, and November, or at least my notices 
/' ' “ ■ “ ^ 7 “““ * ' v ■ uuiuvt j KJ l CSV ICuaL LLl J UOUOVil 
• At e ‘iuently reler to these than any of the other months. 
t is frequently so very loose that it may 
off; in the branches it is sometimes detached 
W ?»« periods 
f ro n , 'Pped oil ; in iuo uvaueues u is suuicumes ueLauneu 
l '81lv o. e ax ‘ s > and elevated into largo cavities which are par- 
., l( with a white granular matter; a section of these 
S l k er efore presents, first, the fleshy crust with its proper 
1,1 < ane ‘ then, the investing membrane of the axis raised 
Na Ce a<5t . w ' t * 1 bbe crust, the white granular matter, and the 
“ r 8n e l be axis itself. Under the microscope, this mem- 
V 0r a Ppears striped and perforated with oval openings; on 
Na|i occasions, in which the membrane was more than 
i 
He 
V 
**e f,' 6 
° f of the' 
S«y s 
* ltac btfie° °^ scure as 10 bid defiance to a separation from its 
tits > at this time the rugae generally are absent and 
tu "uivu *uc< uivuiui uiui v luaii 
V nat tached and fine, the stripes appeared to be com- 
, r ib t °. e ^ u * es similar in shape and arrangement to those 
in ** membrane of the fleshy crust. The oval 
lift »ra . i . f -i. _ _ i 
are continuous with the tubes of the polypes and 
axis, and doubtless serve for the transmission 
to the horny stein. This investing sheath is fre- 
