On the Development o/Ecliinorliynchus gigas. 441 



and an interfibrillar central substance. The first grade occurs 

 frequently in the inner tentacular layer, the second in the outer 

 tentacular layer of Actinia nivea^ Less., and A. effonta^ and 

 almost always in the muscles of the vanes, the third always 

 in the diffused annular muscle of the body-wall, and on those 

 points of it where the septa are attached, and also in the outer 

 tentacular layer of Tealia crassicornis. 



LV. — On the Development o/Echinorhynchus gigas. 

 By Prof. A. Schneidek*. 



The ova of this worm are scattered upon the ground by the 

 pigs. Here they are eaten by the larvae of Melolontha vul- 

 ffaris, and thus arrive at their further development. The ova 

 burst in the stomach of the larva ; and the embryos contained 

 in them can then penetrate, by means of their spines, through 

 the intestine into the body-cavity of the larva ; here they be- 

 come developed, and again reach the intestine of the pig by 

 the agency of the larva. 



The larvffi infested with Echinorhynchi live on until their 

 metamorphosis into cockchafers. As the thorax of the cock- 

 chafer is not unfrequently eaten by man, we can understand 

 that Echinorhynchiis gigas may also get into the intestine of 

 man. It has once been found in that situation by Lambl. I 

 have never succeeded in procuring the development of the 

 embryos of Echinorhynchus gigas either in the larvee of Tene- 

 brio molitor or in Asellus aquaticus. 



When the embryos have aiTived at the body-cavity of the 

 larvee of Ilelolotitha, they remain for some days unaltered and 

 capable of motion ; they then become rigid, acquire an oval 

 form, and envelope themselves in a finely cellular cyst, which 

 is formed of the connective tissue of the larva. The skin of 

 the embryo, with its circlet of spines nt the anterior extremity, 

 continues at first to be the skin of the growing larva ; and it 

 is only at a later period, when the formation of the hooks 

 commences, that it is thrown off, when it forms a second 

 cystic envelope. 



The considerable size and perfect transparency of the larva 

 of EchinorhyncMis gigas permits its development to be more 

 accurately traced than in other Echinorhynchi, the develop- 

 ment of which was first investigated by Leuckart and after- 

 wards by Greef. Here only those facts can be given which 

 are intelligible without figures. 



* Translated by W. S. Dallas, F.L.S., from the 'Sitzimgsbericht der 

 Oberhessischen Gesellschaft fur Natur- und Ileilkuude,' March 8, 1871. 



Ann. & Mag. N. Hist. Ser.4. Fo?. vii. 32 



