432 GROWTH AND STRUCTURE OF T^NIA SAGINATA. 



The first rudiments of the sexual organs appear somewhat early, in 

 about the 200th joint. The processes of formation and growth, as 

 observed by Sommer, are very like those which I stated in the first 

 edition of this work, in regard to T. solium. The full development of 

 the reproductive organs is signalised and completed by impregnation 

 and passage of the eggs into the uterus. These two events are sepa- 

 rated from one another by a distance of about a hundred joints. The 

 development progresses over almost 450 joints, for the first egg in the 

 uterus is observed about the 640th. ^ Shortly before copulation, which 

 takes place at the 516th joint, the porus genitalis and its papilla are 

 formed, whilst the peripheral depression is visible about 100 segments 

 earlier. 



The proper sexual maturity occurs when the chain has acquired 

 about half its total number of joints, at a point which is indeed far from 

 representing the middle of the adult worm, but in fact, in the above- 

 mentioned specimens, lies only about 30 to 38 cm. from the head. The 

 joints concerned are all characterised by a very appreciable and dis- 

 proportionate increase in breadth. 



This state of matters alters as soon as the eggs pass into the 

 uterus. The median canal, which at this time constitutes the whole 

 uterus, stretches out increasingly as it becomes packed with eggs. In 

 consequence of the pressure, the form of the joint becomes approxi- 

 mately rectangular, and that the more markedly, as the number of 

 eggs continues for a good while to multiply, and, with the incipient 

 embryonic development, their size becomes greatly increased. The 

 uterus, however, does not remain a simple tube ; at the 700th joint, 

 at the point where the formerly abundant testes begin to degenerate, 

 a number of protuberances appear at the sides of the tube. These 

 elongate into the space which now becomes free, and as the testes dis- 

 appear, the uterine processes finally occupy the whole space. The 

 eggs continue to be pushed forward on to the 930th joint, up to which 

 point the female germ-producing organs still retain their full develop- 

 ment. Afterwards they too become wasted, and then only do the 

 branches of the uterus begin to assume their final form. At this time, 

 too, one even finds some eggs with hook-bearing embryos; but 

 the number of these is small at first, till 150 segments further back it 

 begins to increase until the 1100th. Here by far the greater number 

 have gone through their primary metamorphosis, and are inclosed in 

 the embryonic shell. 



The full development of both eggs and uterus occurs, of course, 



' My computations differ somewhat, as I have explained, from those of Sommer, 

 who finds the first rudiment of the sexual organs in the 140th joint, the impregnation in 

 the 482d, and the first ooourBffia5«jA|^ffe^n(iAa^araa»im the 581st. 



