402 POLYZOA HYPPOCREPIA. 



cells disposed in quincunx. (Fig. 75.) This arrangement becomes 

 still more apparent on boiling the ovum in alcohol, which however, 

 no otherwise than ether, does not seem to discolour it much. Its 

 brown colour is not owing to the presence of iron, for a long soak- 

 ing of the eggs in prussiate of potass sharpened with sulphuric acid 

 has not communicated the slightest tint of blue to their surface, even 

 when they have been bruised previous to the maceration. Alcohol 

 changes to a golden yellow the original brown colour of the shield. 

 Iodine does not colour, or only colours to a faint yellow, the granules 

 of the perisperm, which their appearance suggested to be amylaceous ; 

 but alcohol separates from them a fatty substance, for, in spontaneous 

 evaporation, this menstruum deposits on the object-glass a white 

 layer over which water glides without raising any thing from it. 



On examining by refraction one of the eggs with a magnifier of 

 one hundred diameters, very often another transparent narrow mar- 

 gin becomes visible, which overlaps all the circumference and 

 indicates an external envelope of extraordinary delicacy. On one 

 side of this there is to be distinguished an evident trace of the old 

 adhesion of the egg to the walls of the tubes which enclosed them, 

 a point which may be called the liilum. Very often, however, this 

 delicate tunic may be sought for in vain on other eggs.* 



32. PLUMATELLA, j" Bosc. 



CHARACTER. Polypidom fixed, membranaceous, confervoid, 

 tubular, branched: Polypes issuing from the extremities of 

 the branches ; tentacular disc of a crescentic form ; tentacula 

 numerous (about 60), arranged upon the margin of the disc in 

 a single series, invested at their origin by a membrane. Allman. 



1 . P. REPENS, polypidom adhering, the erect branches tubu- 

 lar with an entire aperture. (Fig. 76.) Rev. Dr. Fleming. 



Tubipora repens, Lin. Syst. edit. 10, 790. Tubularia repens, Mull. Verm. i. ii. 16. 

 Zool. Dan. prod. 254. Dose Vers, iii. 93. Tub. reptans, Turt. Gmel. iv. 669. 

 Plumatella repens, Lam. Anim. s. Vert. ii. 108 : 2de edit, ii 123. Flem. Brit. 

 Anim. 522. Stark Elem. ii. 441. Landsborougli in Scot. Christ. Herald, n. s. 



* Van Beneden has published a Memoir on the Alcyonella which I have not seen. 

 He finds in the same polype-mass male and female polypes. The embryo young are in 

 a free and isolated state, have a very rapid motion produced by cilia, and simulate 

 Planariae. See Microsc. Journal, ii, 146. 



+ The diminutive of plumata plumed. 



