POLYPIFEUA. 



animal, are prolonged into a common canal, 

 their opposite extremity tapering to a point 

 as the eggs become smaller, each ovary con- 

 taining about sixty eggs. The common tubes 

 of two neighbouring ovaries unite into one as 

 they issue from the longitudinal cavity, and 

 this again joins the common canal of the next 

 pair; the resulting duct, which is thus common 

 to four ovaries, opens into the stomach. The 

 openings of these terminal tubes are arranged 

 in a zig-zag direction, some opening lower 

 down, others higher up. 



Reaumur* believed that the young issued 

 by a slit on each side of the body, situated 

 beneath the fold of the muscular envelope 

 that surrounds the bases of the tentacula, but 

 the supposed openings are merely folds of the 

 skin, never perforate, and not always present. 

 Nevertheless, as the tentacula are perforate 

 at their extremities, and water is frequently 

 forced out of the body through these open- 

 ings, it is possible that some ova may become 

 detached and issue through these organs. 



The ova are round, yellow, and like little 

 grains of sand. Ellis, Reaumur, Dicquemare, 

 and Spix, all assert that Actiniae are vivipa- 

 rous. The latter observer states, " 1 have 

 several times seen them issue from the mouth 

 of their parent perfectly formed. An Actinia 

 that I have in spirit of wine contains a great 

 number of eggs, each marked with an opaque 

 spot that seems to contain the young animal. 

 I have even one individual not larger than a 

 hemp-seed, which seems hardly ready to quit 

 its envelope, having neither the mouth nor 

 the tentacnla perfectly distinct. Moreover, 

 I suspect that the eggs are sometimes hatched 

 in the ovaria or in the stomach, and some- 

 times out of the parent. I am not sure but 

 the animal may at the time of the expulsion 

 of the eggs have its stomach turned inside 

 out." 



The number of eggs must be prodigious, 

 each Actinia possessing upwards of a hundred 

 ovaria. 



It appears from recent researches that the 

 Actiniform polypes are bisexual. 



It is rendered extremely probable by the 

 very advanced condition of the muscular ap- 

 paratus in the Actinia that they likewise 

 possess a nervous system. Spix in his ex- 

 periments employed galvanism, which made 

 the animal contract convulsively, and finding 

 that the contractions were strongest in the 

 neighbourhood of the base of the animal he 

 was led to search for it in this part, and con- 

 ceived that he had discovered it in this situ- 

 ation. " Having raised by a slight incision 

 the longitudinal muscles at their union in the 

 middle of the base, I perceived with a magni- 

 fying glass an interlacement formed by some 

 pairs of nodules disposed around the centre 

 which communicated by several cylindrical 

 threads ; from each nodule two filaments ran 

 forwards ; one was seen to run along the 

 muscle, the other to pierce it, to divide into 



* Histoirc de 1'Acarlemic des Sciences Naturelles, 

 An. 1710. 



two branches, and, lastly, to lose itself in the 

 longitudinal cavity formed by the floating 

 muscles. The situation of the nodules and 

 filaments is beneath the stomach, and their 

 round figure would not allow me to confound 

 them with the muscles, which are broad and 

 riband-shaped, and still less as the latter 

 putrified rapidly, while the former remained 

 entire."* 



Some of the tropical Actinisef, which oc- 

 casionally measure a foot in diameter, pro- 

 duce a stinging sensation when they are 

 handled, and this stinging property is even 

 communicated to the water that they absorb. 

 There is moreover one remarkable circum- 

 stance connected with it ; namely, that it acts 

 much more powerfully upon the skin, which 

 it inflames, than upon the mucous membranes, 

 and a drop received into the eye causes much 

 less pain than when applied to the eyelids. 



The Actinias, although exceedingly vora- 

 cious, will bear long fasting : they may be pre- 

 served alive a whole year, or perhaps longer, in 

 a vessel of sea-water; but when food is pre- 

 sented one of them will devour two mussels 

 in their shells or a crab as large as a hen's 

 egg. In a day or two the shell is voided at the 

 month perfectly cleared of the meat. 



Their power of reproducing lost parts is 

 scarcely inferior to that of the Hydrae. The 

 Abbe Dicquemare j describes some experi- 

 ments on this subject, and states that when a 

 horizontal section is made through one of 

 these creatures the tentacles still seized and 

 swallowed food, which sometimes passed 

 through the body, at other times was expelled 

 from the mouth digested. In about two 

 months tentacles grew from the other portion, 

 and it ate food, soon becoming a perfect ani- 

 mal. He states that in this way he even 

 succeeded in making an Actinia with a mouth 

 and tentacles at both ends ! 



AULOZOA. The third subdivision of PO- 

 LYPI FEU A is composed of a series of zoo- 

 phytes very different in their organisation 

 from those embraced by the two preceding. 

 They have generally been named by natu- 

 ralists Tubular or Vaginated Polypes, and 



are distinguishable from the circumstance 

 that their living substance, instead of being 

 external to the hard polypary, is in them 

 enclosed in a calcareous or corneous tube, 

 sometimes simple, but more frequently rami- 

 fied, from which the polypes are protruded, 

 either through a terminal aperture or from 

 lateral cellules funned by the external en- 

 velope. 



The Autozoa are divisible into several 

 groups, which we shall separately examine, 

 beginning with the Tubular/dee. 



In the Tubnhtna (./%. 48), as in all polypes 

 unprovided with a complete digestive canal, 

 there is an organic portion which brings all 

 the members of the colony into communica- 



* Spix, Ann. du Mus. d'Hist. Nat. vol. xiii. 

 p. 444. 



f Quoy et Gaimard. 

 } Phil. Trans, for 1773. 



