ENTOZOA. 



113 



axis, which continues for five or ten minutes after 

 the death of the bird in which they are developed. 

 Some have supposed that these animalcules 

 were the result of a putrefactive process, but 

 this is disproved by their presence in testicles 

 which have been removed from living animals,, 

 and by their ceasing in fact to exist when the 

 seminal secretion begins to undergo a decom- 

 position. Their extraordinary number is such 

 that a drop of semen appears as a moving mass, 

 in which nothing can be distinguished until it 

 has been diluted as before-mentioned, when 

 the animalcules are seen to disengage them- 

 selves and commence their undulatory move- 

 ments. By means of the continual agitation 

 thus produced the chemical elements of the 

 fecundating fluid are probably kept in a due 

 state of admixture. By the same movements 

 the impregnating influence of the semen may 

 be carried beyond the boundary which it 

 reaches in the female organs from the expulsive 

 actions of the coitus. It has been conjectured 

 that from the rapid and extensive multiplication 

 of these animalcules they may contribute to pro- 

 duce the stimulus of the rut. But the con- 

 sideration of the part which the Zoosperms 

 may play in generation belongs to the Physio- 

 logical history of that function, and would 

 lead to discussions foreign to the present 

 article, which treats of their form and structure 

 simply as the parasites of animal bodies. 



In the human subject the form of the Zoo- 

 sperm is accurately represented in fig. 51. 



Among the cold-blooded Reptiles the Zoo- 

 sperms of the Frog (fig- 51) have been ex- 

 amined with most attention, and have been 

 the subject of interesting experiments in the 

 hands of Spallanzani and Dumas. 



The milt or developed testicle of the osseous 

 Fishes abounds with moving bodies of a glo- 

 bular form. In the Shark and Ray the Zoo- 

 sperms are of a linear and spiral form. 



The molluscous animals are favourable sub- 

 jects for the examination of the present tribe 

 of Entozoa on account of the great relative 

 size of the parasites of the seminal secretion. 

 They are mostly of a filamentary form, and 

 have long been known in the Cephalopods. 

 The Zoosperms of the Snail (Helix Pomatia) 

 present an undulated capillary body, and move 

 sufficiently slowly to permit their being readily 

 followed by the eye. 



The Spermatozoa have been detected and 

 described in the different classes of the Arti- 

 culate Animals. In Insects they are of a fine 

 capillary form, and are generally aggregated in 

 bundles. They abound in the semen of the 

 Anellides and Cirripeds; lastly, these parasites 

 have been found to exist in vast numbers in the 

 spermatic tubes of the higher organized En- 

 tozoa themselves. 



The second tribe of Protelmlntha includes 

 those cylindrical, filiform, eel-like, microscopic 

 Animalcules which abound in decayed vege- 

 table paste, stale vinegar, &c. together with 

 others which have attracted particular attention 

 by the destructive waste caused by certain spe- 

 cies which are parasitic on living vegetables. 

 These animalcules are termed Vibrionida from 



VOL. II. 



their darting or quivering motion. They differ 

 from the polygastric Infusories, not only in 

 the absence of internal stomachs but also of 

 external cilia, which is inferred by their not 

 exciting any currents when placed in coloured 

 water. They present a higher grade of organi- 

 zation than the Cercarian tribe in the presence 

 of a straight alimentary canal, which is re- 

 markably distinct in some of the higher forms 

 of the group, as the Gordioides and Oxyu- 

 roides of Bory St. Vincent. 



The higher organized Vibriones have distinct 

 generative organs, and are ovo-viviparous. 



In the species of Vibrio which infests the 

 grains of wheat and occasions the destructive 

 disease called Ear-cockle or Purples, Mr. Bauer 

 found the ova arranged between the alimentary 

 canal and the integument, in a chaplet or 

 moniliform oviduct which terminated by a 

 bilabiate orifice at a little distance from the 

 caudal extremity of the body. The ova are 

 discharged at this orifice in strings of five or 

 six, adhering to each other. Each egg is about 

 5^jth of an inch long, and g^th or g ^th in di- 

 ameter: and they are sufficiently transparent 

 to allow of the young worm being seen within : 

 and the embryo, in about an hour and a half 

 after the egg is laid, extricates itself from the 

 egg-coverings. Of the numerous individuals 

 examined by Mr. Bauer, not any exhibited 

 external distinctions of sex, and he believes 

 them to be hermaphrodites. 



In the Anguillula aceti, or common Vinegar- 

 eel, Bory St. Vincent has distinguished indi- 

 viduals in which a slender spiculum is pro- 

 truded from the labiate orifice corresponding 

 to that above described from which the ova 

 are extruded ; these individuals he considers 

 to be males ; they are much less numerous 

 than the females; are considerably smaller; 

 and the internal chaplet of ova is not dis- 

 cernible in them. In the female the ova are 

 arranged in two series on each side of the 

 alimentary canal, and the embryo worms are 

 usually seen to escape from the egg-coverings 

 while yet within the body of the parent, and 

 to be born alive. Ehrenberg figures the two 

 sexes of Anguillula fluviatilis in his first trea- 

 tise on the Infusoria (tab. vii. fig. 5.*) The 

 granular testis and intromittent spiculum, which 

 is single, are conspicuous in the male ; the ova 

 in the female are large and arranged as in 

 Anguillula aceti. Such an organization, it is 

 obvious, closely approximates these higher 

 Vibrionidae to the nematoid Entozoa, as the 

 Ascarides and Oxyuri, and further researches 

 on this interesting group will doubtless lead to 

 the dismemberment of the Oxyuroid family 

 from the more simple Vibrionida, as the 

 genera Bacterium, Spirillum, and Vibrio, with 

 which they are at present associated. 



To the group composed of the three last- 

 named genera, the microscopic parasite of the 

 human muscles, termed Trichina Spiralis, is 

 referrible.f 



* Organisation, systematik und georaphisches 

 Verhaltniss der Infusionthieschen, 1&30. 



t Zool. Trans, vol. i. r>. 315, and Zool. Pro- 

 ceedings, for February, 1835. 



I 



