ENTOZOA. 



139 



P 'lunar 'KB in the species Planaria torva. Upon 

 separating the individuals, he perceived a long 

 white tube projecting from the genital pore of 

 each, proving the reciprocity of fecundation. 



Notwithstanding the complicated apparatus 

 above described, the Planaria; are remark- 

 able for their spontaneous fissiparous gene- 

 ration, and the facility with which detached 

 or mutilated parts assume the form and func- 

 tions of the perfect animal. Fig. 92, o, repre- 

 sents a Planaria lactea, with the anterior part 

 of the body artificially divided in the longitu- 

 dinal direction ; jig. 92, E, shews the same in- 

 dividual having two perfect heads, the result 

 of the preceding operation. 



The female generative orgrans of the Lingua- 

 tula ( Pentasloma) t&nioides present a struc- 

 ture in some respects analogous to that of the 

 Di$loma perlatum : the ovary (n, n,jig. 78) 

 is a part distinct from the tubular oviduct, 

 and is attached to the integument or pa- 

 rietes of the body, extending down the 

 middle of the dorsal aspect. It consists of 

 a thin stratum of minute granules ; clustered 

 in a ramified form to minute white tubes, 

 which converge and ultimately unite to form 

 two oviducts (o, o, Jig. 78). These tubes pro- 

 ceed from the anterior extremity of the ovary, 

 diverge, pass on each side of the alimentary 

 canal, and unite beneath the origins of the nerves 

 of the body, so as to surround the oesophagus 

 and these nerves as in a loop. The single tube 

 (p) formed by the union of the two oviducts 

 above described, descends, winding round the 

 alimentary canal in numerous coils, and ter- 

 minates at the anal extremity of the body. The 

 single oviduct, besides receiving the ova from 

 the two tubes (o, o), communicates at its com- 

 mencement with two elongated pyriform sacs 

 (tn y m), which prepare and pour into the ovi- 

 duct an opaque white secretion. These bodies, 

 from their analogy to the impregnating glands 

 in the Trematoda, I was led to regard (in the 

 description, published in the Zoological Trans- 

 actions, of the only individual of this interesting 

 species that I have hitherto been able to pro- 

 cure for dissection,) as testes, and the gene- 

 ration of the Linguatula to be androgynous, 

 without reciprocal fecundation ; individuals, 

 however, of the male sex have since been de- 

 scribed in this species by Miram* and Diesing. 



The male Lingiiatula is, as in dioecious 

 Entozoa generally, much smaller than the 

 female: the generative apparatus consists of 

 two winding seminal tubes or testes, and a 

 single vas deferens, which carries the semen 

 from the testes by a very narrow tube, and 

 afterwards grows wider. It communicates 

 anteriorly with two capillary processes, or 

 penes, which are connected together at their 

 origin by a cordiform glandular body, repre- 

 senting a prostate or vesicula seminalis. The 

 external orifices of the male apparatus, accord- 

 ing to Miram, are two in number, and are 

 situated on the dorsal aspect of the body, just 

 behind the head. 



Diesing, however, describes the male Pen- 



* Nova Acta Acad. Naturae Curios, torn. xvii. 



Fig. 93. 



tastoma as having only a single penis, which 

 perforates the interspace between the second 

 and first segments of the body, and protrudes 

 below and behind the oral aperture. 



Much interest attends the consideration of 

 the reproductive organs of the dioecious En- 

 tozoa, since they are the first and most simple 

 forms of the animal kingdom which present 

 that condition of the generative function. In the 

 Acanthocephala the structure of the generative 

 apparatus has been ably elucidated by Cloquet 

 in the species which commonly infests the 

 Hog, viz. the Echinorhynchus gigas. The male 

 organs consist of two testes, two vasa defe- 

 rentia, which unite together to terminate in a 

 single vesicula seminalis, and a long penis 

 gifted with a particular muscular apparatus. 

 The testes (/, A, fig. 93) are cylindrical 

 bodies, pointed at both ex- 

 tremities, of nearly the same 

 magnitude, but situated one 

 a little anterior to the other. 

 The anterior one is attached 

 by a filamentary process (g) 

 to the posterior extremity of 

 the proboscis : the posterior 

 gland is connected by a 

 similar filament to the in- 

 ternal parietes of the body. 

 The vasa deferent ia (I), 

 after their union, form seve- 

 ral irregular dilatations (A:), 

 which together constitute a 

 lobulated vesicula seminalis. 

 This reservoir is filled with 

 a white grumous fluid like 

 that which is found in the 

 testes, and it is embraced 

 posteriorly by the retractor 

 muscles of the penis (r, r), 

 which form a kind of coni- 

 cal sheath for it. 



A small, firm,white, and 

 apparently glandular body 

 (q} is situated at the point 

 of union between the vesi- 

 cula seminalis and the 

 penis. 



The penis is a straight, 

 cylindrical, firm, white or- 

 gan, and in the retracted 

 state is terminated by a di- 

 lated portion (o), occupying 



the posterior extremity of 

 ^ body> but which d]Sap _ 



pears when the intromittent 

 organ is protruded. This 

 action is produced by the muscles s, s, when 

 the penis presents the form of a short broad 

 cone, adhering by the apex to the caudal 

 extremity of the body: it is retracted by the 

 muscles r, r, above described. 



The female organs consist of two ovaries 

 and one oviduct. The former are long and 

 wide cylindrical canals, which of themselves 

 occupy almost the whole cavity of the body 

 extending from the proboscis to the tail (h, h, 

 jig. 83). They are situated, one at the ventral, 

 the other at the dorsal aspects of the body, arid 



"\ t 



T 



Male organs of gene- 

 ration, Echinorhyn- 

 chus gigas. 



