KIiTO'/.OA. 



1 r: 



I :n uva of llie greater part ol the TftHtatoda 

 IN i \rluded |inni In '.lie lull development of the 

 lii-tiis ; they U nl ;in n\.il lint some- 



times spheneal fin in, null many nl ' 

 larly rcscml. 1 or capsules of c-cri.iin 



mosses, in having a small circular portion of 

 ifce OUttf Covering sepUBte from tin- H---I, anil 

 closing the cavity of the cug hki- a lid. 



ISorilmann lias studied ilic development of 

 the young of the Distoinu /linns, which infest 

 tin 1 intestines of the perch. According to this 

 < vci -lli-iit observer the foetus raises, in its en- 

 deavours tci slip out of the egg, the small lid, 

 ami writhes about for some time, being still 

 attached to one point of the egg. In about 

 six hours it succeeds in freeing itself from 

 the egg-coverings; and at this period it differs 

 in every respect from the shape of the parent 

 animal ; the body, which is of a mucous con- 

 sistence and perfectly transparent, is of an oval 

 form ; the anterior mouth forms a small square- 

 shaped projection, and the whole surface 

 of the body is beset with many longitudinal 

 rows of short cilia, which are in rapid and 

 incessant motion, and create a vortex in the 

 surrounding water, similar to that which the 

 I'nlygastric Infusoria produce. The little 

 animal having its anterior extremity diminish- 

 ing to a point, is well formed for swimming, 

 and by means of its vibratile cilia, quickly 

 darts out of the field ot vision when under the 

 microscope. At the distance of one-third of 

 tin- body from the anterior extremity there is 

 u single coloured eye-speck, from which, when 

 pressed between glass plates, there escapes 

 a brilliant blue-coloured pigment. Thus orga- 

 nized, the young of the intestinal parasite just 

 described move to and fro in water as if this 

 were their natural element, and approximate 

 in form and structure most closely to the Poly- 

 uastric Infusoria of the genus Ptiramifcium, 

 J.lnvnb. Jn this state, doubtless, they are 

 eji-i i,-il by the Fish, in the intestines of which 

 they were originally developed, into the sur- 

 rounding water,and wheiiagain received into the 

 alimentary canal undergo their metamorphosis, 

 lose, like the Lerin-a- ami (impedes, the organ 

 ot MSIOII which guided toe movements of their 

 young and free life, and grow and procreate 

 at the, expense of the nutrient secretions with 

 which they are now abundantly provided. 



Ju the Cif/fliniiithn the young cast their in- 

 leumreM, and would stein in some species, 

 a I'M l''i/,u in Mii/tii< nsis, to undergo a change 

 in the form and proportions of the extremities 

 of the body, but they do not possess cilia or 



, as in the Tremaloda above-mentioned. 

 The ova of the iMgH&tula are of an oval 

 form : the germinal vesicle is situated near the 

 .ides hall-way between the two extremi- 

 ties: the \iteilnie membrane is surrounded 

 v. it. i a ttrong eortical membrane : the develop- 

 ment of tin- I'u tus takes place out of the body. 

 In the Strnagylut gigtt, Slroii^if/Hs iw//i.r\, 

 and .! if 'i ,/!, IMIMIM in), -stiiii: the in- 



testines of the G<MtMickw ( we have found the 

 fatus completely formed in the ova contained 

 in the uterus or terminal Moment of tin 

 latixe tube, while those in the ovary or narrow 



commencement of the same part were still . 

 pied with the granular in .- vitellns 



The mature out of the .S//< 

 of an el 1 1 pi leal form, and tin - ithm 



is plainly seen coiled up through the i 

 parent coats of theegg; the res. -mlilam-e which 

 these bear to the 'ineliinii when inclosed in 

 its inner cyst is very striking: tin- hypothesis 

 suggested by this resemblance need only lie 

 alluded to for the purpose of exciting the at- 

 tention of those, who may hereafter meet with 

 the preceding minute muscular parasite, to the 

 existence of larger Nematoid Kntozoa in other 

 parts of the body. 



Cloquet describes the ova in the beginning 

 of the ovaries of the Ascura Lumbricoutes as 

 consisting of rounded linear corpuscles, 

 pointed at one extremity, thickened at the 

 other; in the middle of the ovaries they as- 

 sume an elongated triangular form, and one 

 of their angles frequently supports a small 

 spherical eminence; the base of the ovum 

 adheres to the parietes of the oviduct, the apex 

 projects into its cavity. In the enlarged canals, 

 which he terms the cornua of the uterus, the 

 ova are unattached and of a conoid or irre- 

 gularly triangular figure. In the uterus itself 

 they have assumed an ovoid or elliptical form, 

 are surrounded by a transparent glairy mucus, 

 and are composed of a transparent cortical 

 membrane, perfectly smooth on the external 

 surface, and filled with a transparent fluid, in 

 which floats a linear embryo, disposed either 

 in a straight line or coiled up. Cloquet never 

 observed the young Ascarides excluded from 

 the egg in the interior of the uterus, and we 

 equally searched in vain for free embryos in 

 the generative tubes of the Strongylus and 

 Oxyurus above-mentioned, although their de- 

 velopment in regard to form appeared to be 

 complete in the ovum ; the structure of the 

 embryo resembles that of the simpler Vibriones, 

 there being no generative tubes apparent, and 

 the cavity of the body being occupied by a 

 granular parenchyma. 



With respect to the exclusion of the ova 

 in these ana similar ovo-viviparous Nematoid 

 Kntozoa, it would appear to be very commonly 

 accompanied with a rupture of the parietes 

 of the body and of the generative tube. Ru- 

 dolphi observes, with respect to the Cucullanus, 

 " ( h nla, verine quieto, per intervalla ex vulva 

 pullulent ; ([inn eodem disrupto, quod sa-pe 

 accidit, ovula vel embryones ex ovariis pro- 

 lapsis parituque rtiptis vi quadam et undatim 

 protroduntur." 



The generation of the Filiiria ^[edinenlu is 

 of the viviparous kind, and the progeny is 

 countless, " Filaria? nostra," observes Kudol- 

 phi, " prole quasi farctae stint, quod si harum 

 longitudinem illius vero minutiem spectas, 

 fatmmi miiHa millium millia singulis tnbuit." 

 What is most remarkable is, that the 

 bryos are not, as in the Strnni/lus and the 

 Nematoid genera above-mentioned, eir - 

 in an eire-covering, <nor are they included in a 

 . i ame tube, but float freely along 

 with a uiaiinlai substance in the common mus- 

 cular envelope of the cavity of the body. 



