ENTOZOA. 



141 



the gut, as it descends, gradually enlarging, to 

 the lower part of the intestine, where it sud- 

 denly contracts and runs down, as a very slender 

 canal, to near the vulva. It is partly covered 

 by two long slender bodies of a horny sub- 

 stance, representing a bifurcate penis. 



From this comparison of different genera 

 of the Nematoidea, it is seen that, althoug 

 there are many varieties of structure in tl 

 efferent and copulative part of the male gene- 

 rative apparatus, the essential or secerning por- 

 tion uniformly consists of a single tube. A 

 like uniformity of structure does not obtain in 

 the essential parts of the female organs : in a 

 few instances the ovary is single, correspond- 

 ing to the testis in the male, but in the greater 

 number of the Nematoid worms it consists of 

 two filamentary tubes. 



The Strongylus gigas is an example of the 

 more simple structure above alluded to. The 

 single ovary commences by an obtuse blind 

 extremity close to the anal extremity of the 

 body, and is firmly attached to the termination 

 of the intestine ; it passes first in a straight line 

 towards the anterior extremity of the body, 

 and when arrived to within a short distance 

 from the vulva, is again 

 Fig. 95. attached to the parietes 



of the body, and makes 

 a sudden turn back- 

 wards (f,Jig. 95); it 

 then forms two long 

 loops about the mid- 

 dle of the body and 

 returns again forwards, 

 suddenly dilating into 

 an uterus (e), which is 

 three inches in length, 

 and from the anterior 

 extremity of which 

 a slender cylindrical 

 tube, or vagina, about 

 an inch in length, (e,d, 

 Jig. 95) is continued, 

 which after forming a 

 small convolution ter- 

 minates in the vulva, 

 at the distance of two 

 inches from the ante- 

 rior extremity of the 

 body. Rudolphi was 

 uncertain as to the ter- 

 mination of the ovi- 

 duct in the Strongylus 

 gigas, and Professor 

 Otto, who appears to 

 have mistaken its blind 

 commencement for its 

 termination, believed 

 that the oviduct opened 

 into the rectum. 



The theory which 

 had suggested itself to 

 Rudolphi of the corre- 

 lation of a simple ovi- 

 Anterior extremity of the duct in the female with 

 Strongylus gigas, showing t] sp i cu l um s i mp l e x 

 the commencement of the c , r j r 



digeMreand the teriina- f the male, and of a 

 tion of the generative tube, double OVlUUCt With 



the spiculum duplex, receives additional dis- 

 proof from the circumstance of the uteri and 

 oviducts being double in the Strongylus in- 

 Jie.vus and Strongylus armatus. In the former 

 species (which infests the bronchial tubes and 

 pulmonary vessels of the Porpesse, and which 

 I once found in the right ventricle of the heart 

 of that animal,) each of the two female tubular 

 organs may be divided into ovary, oviduct, 

 and uterus : the ovary is one inch in length, 

 commences by a point opposite the middle 

 of the body, and, after slightly enlarging, 

 abruptly contracts into a capillary duct about 

 two lines in length, which may be termed the 

 oviduct, or Fallopian tube, and this opens 

 into a dilated moniliform uterus three inches 

 in length ; the divisions here described were 

 constant in several individuals examined, and 

 cannot, therefore, be considered to result from 

 partial contractions. Both tubes are remark- 

 ably short, presenting none of the convolutions 

 characteristic of the oviducts of Ascaris and 

 Filaria, but extend, in a straight line, (with 

 the exception of the short twisted capillary 

 communication between the ovaria and uteri,) 

 to the vulva, which forms a slight projec- 

 tion below the curved anal extremity of the 

 body. 



The reason of this situation of the vulva 

 seems to be the fixed condition of the head 

 of this species of Strongylus. In both sexes 

 it is commonly imbedded so tightly in a con- 

 densed portion of the periphery of the lung as 

 to be with difficulty extracted ; the anal extre- 

 mity, on the contrary, hangs freely in the 

 larger branches of the bronchi, where the 

 coitus, in consequence of the above dispo- 

 sition of the female organs, may readily take 

 place. 



In the Strongylus armatus the two oviducts 

 terminate in a single dilated uterus, and the 

 vulva is situated at the anterior extremity of 

 the body, close to the mouth. 



We find a similar situation of the vulva in 

 a species of Filaria, about thirty inches in 

 length, which infests the abdominal cavity of 

 the Rhea, or American Ostrich. The single 

 portion of the genital tube continued from the 

 vulva is one inch and a quarter in length ; 

 it then divides, and the two oviducts, after 

 forming several interlaced convolutions in the 

 middle third of the body, separate ; one ex- 

 tends to the anal, the other to the oral ex- 

 tremities of the body, where the capillary 

 portions of the oviducts respectively com- 

 mence. 



In the Ascaris Lumbricoides the female organs 

 (Jjg. 96) consist of a vulva, a vagina, a uterus, 

 which divides into two long tortuous oviducts 

 gradually diminishing to a capillary tube, 

 which may be regarded as ovaries. All these 

 parts are remarkable in the recent animal 

 for their extreme whiteness. The vulva (</, 

 Jig. 72,) is situated on the ventral surface of 

 the body at the junction of the anterior and 

 middle thirds of the body, which is generally 

 marked at that part by a slight constriction. 

 The vagina is a slightly wavy canal five or six 

 lines in length, which passes beneath the in- 



