THE CYSTIC ENTOZOA. 53 



striking proof of this is offered by the Cyslicercus cellulosce, of 

 which the diagnosis invariably states, that it possesses a "vesica 

 caudalis, elliptica, transversa." This form of caudal vesicle is, 



however, only found in such Cys- 



Fig. 27. Fig. 28. ticerci as are imbedded in the mus- 



- cles of men and pigs ; in individuals 



/? r ~~~ of the same species residing within 



U SL=dHfc the human brain, the caudal vesicle 



^^BI0I^^B^li^kv^^B 



assumes the most various and irre- 

 gular forms (figs. 24, 27, 28). Even 



in the Tcenia-scolex observed by Stein, 1 the caudal appendage 

 of the receptacle assumed the greatest variety of shapes. 



If attention had been earlier directed to these circumstances, 

 the cystic Entozoa would not have been made into a separate 

 order from the Cestoidea. The older naturalists and helmin- 

 thologists took a far more just and unprejudiced view of the 

 matter, when, from the similarity of the degenerated cystic 

 scolices with the heads of certain Cestoidea, they divined the 

 close connection of the two orders, and described the Cystica as 

 Tcenia vesicularis, Tcenia hydatigena, Tcenia cellulosce. Even the 

 dropsical condition of these cystic worms did not escape the eyes 

 of the older naturalists, since already, in 1691, Tyson 2 described 

 the Cysticercus tenuicollis as Lumbricus hydropicus. 



But after Linnaeus had animated naturalists with his spirit of 

 arrangement, they worked with such good will and so exclusively, 

 at the perfection and completion of his system, that for a long 

 time it seemed to be thought enough if generic and specific 

 names were given to newly discovered animals, and their due 

 systematic place assigned. The inquiry into the natural history 

 of these animals hence became quite a secondary consideration, 

 and with such a one-sided study of animal forms, it could hardly 

 fail to happen that not merely varieties, but also young states, 

 larvae, and even fragments of animals already known, should be 

 described and systematically arranged as peculiar animals. 3 



Figs. 27, 28. Two Cysticcrci rendered quite irregular by constriction of their 

 vesicles ; from the human brain, natural size. b. The retracted anterior edge of the 

 scolex. In fig. 28 the constricted parts are produced into tubes. 



1 See ' Zeitschrift fiir Wiss. Zoologie,' Bd. iv, 1853, p. 207, and pi. x, figs. 12 14. 



2 ' Philosophical Transactions,' 1691, No. 193, p. 506, figs. 1 4. 



3 Ehrenberg's and Diesing's systematic works on Infusoria and Entozoa, testify that 

 this faulty and one-sided method finds followers even now. 



