218 



GENERAL ORNITHOLOGY. 



of appearance as they present umlev difl'erent circmnstauces is mainly seasonal. For birds, 

 as a rule, procreate only at particular times of the year, rarely luuing more than one or 

 two broods of youne; ; the functional activity and quies<-ence of the testes correspond, as the 

 enormous swelling of the gland during the breeding season is one of the peculiarities of the 

 bird's orgau. This may be related to the absence, hi birds, of specially formed vesicular semi- 

 ■iiales, or seminal reservoirs; though certain contortions and dilatations of the sperm-duets 

 which are to be observed may imperfectly answer to detain the secretion until circumstances 

 render it available. The jiassage of the sperui-duct is along the face of the kidneys, generally 

 in company with the uretei's ; tlie opening is by a papilla upon the surface of the uro-genital 

 sinus. These ])apillose terminations of the sperm-ducts are erectile to a degree, and answer the 

 purpose of paired penes in those birds wluch are not provided with better-formed copulatory 

 parts. Li coitii, the cloacal chambers containing the orifices of the genital ducts are opened, 

 and the more or less protruded jiapillie come in contact or close juxtaposition. In cases in 

 which a penis or two penes are developed, the urethral passage is a grotive, never a tube, 

 though cavern(_>us and even muscular tissue may be developed ; and iu any case of such au 

 intromittent apparatus, it has cloacal invagination when not operative (see p. 6S0). These 

 organs, in all their variet)-, are of the sauropsidan, not mammalian, type ; though in some 

 respects the structure approaches that seen in the non-placental manmials. Xo prostate or 

 cowperian glands exist in birds. 



The sole office of the testis, or oijphoron mascuVtniim, is the secretion of semen, associate 

 structures being simply accessory, for the conveyance i^f that vital substance and its transfer- 

 ence to the opposite sex. The seminal fluid itself is merely the vehicle of transport of the 

 spermatozoa, in which their activity may be freely exercised in their intuitive struggles to gain 

 access to then- mates in the ovary. It is literally a " sea of life " in which the minute creatures 

 swim in shoals to their destiny, — and tlieir fate in any case is death. If they successfully 

 buffet the waves of fate they find a \vatrry grave iu the ovum at last ; if that haven be not 

 reached they simply perish iu mid-ocean. The spermatt)Zoa, ca seminal animalcules, or male 

 Dijnamama;ha: (figs. 106, 107), are the exact counterparts of ovarian ova, in so far as they are 

 single-celled animals of a very low grade of organi- 

 zation ; but their activity and intelligence is marvel- 

 lous, and still more so is the mysterious attribute 

 M"ith wliich they are endowed iif assiuulating their 

 protoplasmic substance "M-ith that of the ovum; with 

 the result that the thus fecundated ovum is capable 

 of procreating itself by fission for a period until a 

 nuiss of similar creatures is engendered; from which 



Fig. 106. -Spermatozoa ujj^ss jg (hen speedily evolved the complex body of ^.^u^^'^'Uf'^rrZ- 

 of .lomestic cock, greatly , .,,. , „„ ' ,. ,. , t, matozoaol spariow, 



inaffnifled; from Owen, after the JBud. i he corresponding female i)//)(o;«<://Ha'6ff' greatly magnibed; 

 Waguer and Leuckart. (ovarian ova) are simple spherical animalcules, phys- Wa^nerlndLe'uck- 



ically indistinguishable from an ordiuary encysted ^lH(a"6fl' .• but the sperma- art. 

 tozoa are remarkalily distinguished in appearance, furuishiug probably the best marked case of 

 sexual characters to be found among the Protozoa, to which class of animals they belong. The 

 spermatozoa resemble flagellate infusoria or ciliated endothelium cells, though they each have 

 but a single whip. They are of extremely minute size, much smaller than their females, and 

 filamentous; more or less thickened and sometimes wavy at their nucleated heads, whence pro- 

 trudes an excessively delicate thready tail, endowed with great vibratory energy. They may be 

 likened to diminutive attenuated tadpoles, which swim by lashing the tail iu the seminal fluid. 

 Under the microscope shoals of these curious creatui'cs may be seen swimming in the sea, nosing 

 ab(iut in search of the ovum, butting their heads in wrong places, backing out and trying again 

 in another direction; with such success that out of myriads a score or so may gain their end. It 



