DESCEIPTION 01^ PLATES. XXV 



PLATE XVII. 



PIG. 



1. Nucleated germs fromthe coecal extremity of the ovarian tube otAscaris mystax. 



2. Pedunculated ova at an early stage of development. 



3. Two similar ova of a triangular form and further advanced. 



4. TJnimpregnated ovum still further developed. 



5. Ovum " duriug fertilization, whose vitellus is much broken up by the sper- 



matic particles." 

 6 — 17. Impregnated eggs in various stages of development during the process of 

 yelk-segmentation. 

 18 — 24. Sumlar series, showing the finely granular yelk gradually developing 

 itself into a vermiform embryo. 

 The above figures are from Nelson ; beiug the same as those selected by Prof 

 J. Hughes Bennett to illustrate his first Lecture " On Molecular Physiology," etc., 

 published in the " Lancet," for Jan. 3rd, 1863. Figs. 1—3 are X 330 diam. ; the 

 remainder x 220 diam. 



PLATE XVIII. 



Head of Oxyuris vermicularis, showing the exserted trilobular lip, the com- 

 mencement of the pharynx, the transverse lines, and, more particularly, the 

 lateral winged-appendages (X 220 diam.). 



Head, neck, and upper part of the body of the same, exhibiting the retracted 

 mouth, the lateral alee, the transverse markings of the iutegiiment, and, 

 more especially the pharynx, oesophagus, and upper part of the intestinal 

 canal (x 220 diam.). 



Section of the body of the same, showing ova within the uterine canal, and 

 the mode of termination of the vaginal passage (x 110 diam.). 

 These figures are from drawings by Mr. Busk. 



PLATE XIX. 



1. A female Oxyuris vermicularis, displaying the normal position of the digestive 



and reproductive organs, and the points at which their several outlets 

 terminate (x 20 diam.). 



2. Oral extremity of the same, showing the partly protruded lips, the lateral alee, 



and pharyngeal muscles (x 450 diam.). 



3. Section from the lower part of the body, exhibiting the mode of termination of 



the intestinal canal, and, more particularly, numerous ova lodged within, in 

 the folded extremity of one of the uterine horns (x 220 diam.). 



4. Four ova ; a, showing the commencement of the embryonic formation, and 



h, c, d, the completed tadpole-shaped embryo in their interior (x 450 

 diam. ) . — Original. 



Figs. 1 to 3, inclusive, are from drawings by Mr. Busk. 



d 



