VERMES. 



bably refplre by this part : but the zoophytes, properly fo 

 called, begiiming willi the armed polypes (hydra;, breathe, 

 if at all, by their whole furface. 



If, as fome have conjeftured, the vibrating organs of the 

 vorticellx and rotifers are an apparatus for breathing, thefe 

 animals ought to occupy a higlier rank in the fcale of being 

 than they do now. Their extreme minutenefs mull oppofe 

 great obilacles to our acquiring any exaft knowledge about 

 them. 



Phyfwh^y of Refpiratlon. — The changes produced in the 

 air by the refpiration of the moUufca, &c. have been 

 already fpoken of in the article Respiration, towards the 

 end, under the head of Refpiration of Animals. We have 

 only to notice here the fads that have been afccrtained re- 

 fpefting their temperature. 



" Spallanzani obferves," fays Mr. Ellis, " that when a 

 fnail or (lug is infulated in a jar of atmofpheric air, a ther- 

 mometer placed in the jar will continue ftationary ; but 

 when feveral are confined together, the mercury rifes one- 

 tenth, one-feventh, and even one-fifth of a degree, and in 

 oxygen gas, one-third of a degree ; from which he con- 

 cludes, that fnails and flugs, in decompofing oxygen gas, 

 give out caloric enough to be fcnfible to the thermome- 

 ter. (Memoirs on Rt-fpiration, p. 255. 258.) This ex- 

 periment we repeated, by confining feveral fnails in a pint 

 jar of air, from the top of which a fmall thermometer was 

 fufpended, and at the bottom a glafs of lime-water was 

 placed. A film of carbonate of lime foon overfpread the 

 lime-water, the infide of the jar was dimmed by moifture, 

 and the mercury in the thermometer rofe at the fame time 

 nearly one degree. Dr. Martine fays, that from the refult 

 of feveral trials which he made, fnails were about two de- 

 grees warmer than the air. (On Thermometers, p. 141.) 

 Mr. Hunter found the lungs of fnails 38°, when the at- 

 mofphere was 34° ; and, in other inftances, fnails were fix 

 and feven degrees above the atmofphere, when it was fo low 

 as 30''. Earth-worms he found ^^•°$, when the atmofphere 

 was 56'' ; and, in other trials, the worms exceeded by four, 

 leeches by three, and flugs by four degrees the temperature 

 of the ambient air. (Treatife on the Blood, p. 298, ct leq.) 

 The temperature of a fnail, which was 44", fank, on expo- 

 fure to a cold mixture, down to 31°, and then froze; and 

 feveral leeches froze hkewife when reduced to 31°. (Ob- 

 fervations on the Animal Economy, p. 105.) In all thefe 

 experiments, the animals, when thawed, were found to be 

 dead ; but Mr. Carlifle fays, that the garden-fnail may be 

 frozen, during its (late of dormancy, without dellroying its 

 mufcular irritability. Diilof Tranf. 1805, p. 18." In- 

 quiry into the Changes, &c. p. 215. 



Generative Organs. 



Generative Organs of the MoUufea. — Four combinations 

 are met with in this clafs : t/'k. i. Separate fexes with 

 copulation ; in feveral gaileropoda, as the buccinum. 



2. Separate fexes without copulation ; in the cephalopoda. 



3. The fexes united with reciprocal copulation ; in the 

 fnail, and moft gaileropoda. 4. The fexes united, and 

 fecundating each other in the fame individual, or perfeft 

 hermaphrodifm ; in the acephala. 



The Cephalopoda ; Male Organs. — The tefticle is a large, 

 wlntifli, and rather foft gland, found in the bottom of the 

 abdominal fac ; its (lru£lure is remarkable, and eafily deve- 

 loped. It is inclofed in a membranous capfule, united to it 

 only by vclTels paflfing between them, and that at one point 

 only : it has a thin proper cellular tunic. Its furface ex- 

 hibits an infinite number of fmall areoli, which are the com- 

 mencement of white, opaque, loft filaments, lying clofc to- 



gether and compofing the whole fubllance of the gland. In 

 the cuttle-fifli thefe filaments are fmall and numerous, fo that 

 the areola- are mere points. In the oftopus the filaments 

 are larger, and like ribbons. They unite fuccefTively to form 

 trunks, which terminate in the cuttle-fifh, in va(l numbers, 

 in three or four large excretory canals pafling through the 

 gland in various diredlions, alid ending ultimately in a large 

 common circular opening, furnilhed with a valve which pre- 

 vents the return of the fluid. In the odlopus, which has 

 fewer filaments, the large common canals do not exift, but 

 the filaments end immediately at the common opening. Thefe 

 filaments are themfelves 'fmall excretory velTcls, furrounded 

 by glandular parenchyma, and connefted by blood-veffels, 

 nerves, and cellular fubllance. The fluid they fecrcte is 

 poured out through the opening into the membranous cap- 

 lule, from which it is conveyed by a canal rcprefenting the 

 epididymis, and tortuous, like that tube in the human fub- 

 jeft. It ends in a larger canal, of which the interior has at 

 firfl feveral projefting and ramified columns and ridges, and 

 afterwards a fingle one extending through its whole length, 

 and dividing it into two half canals. This canal, much 

 fhorter and lefs tortuous than that of the epididymis, con- 

 trafts towards its end, and penetrates a tolerably large cy- 

 lindrical glandular body, poffefTrng a large excretory duft, 

 which receives the termination of the canal jull mentioned. 



This body is large and folid in the oftopus, much lefs 

 and nearly membranous in the cuttle -fi(h. It is regarded as 

 a kind o( proftate. Its canal joins one of the two belong- 

 ing to the cavity which contains the fpringiug tubes, which 

 will be fpoken of prefently. 



This cavity or burfa, which is large and much folded, is 

 capable of confiderable extenfion, and contains the cele- 

 brated tubes, firit imperfeftly defcribed in the cuttle-fifh 

 by Swammerdam, then more in detail' by Needham in the 

 calmar, and rendered famous by BufFon, who derived from 

 them the principal fupport of his fyllem, on the nature of 

 the fpermatic animalcules. The o6lopus lias them larger 

 than the two other fpecies. The burfa, which contains 

 them mixed up with a vifcid liquor, is compofed of two 

 compartments communicating together, but each poffeffing 

 a dillinft orifice. One of tliefe orifices is the commence- 

 ment of a (lender canal, which ends on the exterior of the 

 penis at the fide : the other alfo produces a canal, which, 

 after having become Rill fmaller, opens externally near the 

 bafe of the penis. 



The penis is a hollow, cylindric.il, flefhybody, perforated 

 at Its point, and h.aving a cul-de-fac behind the place where 

 the canal jull mentioned opens. Its cavity poflelfes flefliy 

 col.imns internally. 



The excretory canal of the proftate, which is to tranfmit 

 alfo the feminal fluid of the tefticle, communicates more 

 particularly witii that compartment of the burfa, whofe duft 

 opens externally on the penis. The communication indeed 

 is very near its orifice. It is the other compartment of the 

 burfa, whofe duft opens in the penis. The name of penis 

 is given to this part, becaufe it projcfts externally, and 

 has a cylindrical form : it does not fecm, however, to 

 be an organ of copulation, although it certainly is one of 

 ejaculation. 



All the canals now defcribed, from the tefticle to the 

 penis, are fituated on the left fide of the abdomen, and the 

 penis projefts witliin the left branchia ; but as tlie funnel 

 placed under the neck clofes the flclhy bag, it frenis impof- 

 ilble for the penis to approach the part which gives Iffue to 

 the oviduft of the female, fo as to produce copulation. 

 The feminal fluid thrown out by the penis muft. travcrfe the 

 funocl, as the ova, the ink, and the excrements do. 



Swam- 



