Miscellaneous. 233 



The oesophageal commissures are pretty strongly developed. The 

 ventral cord presents two closely approximated longitudinal com- 

 missures, with a considerable number of ganglionic dilatations, 

 which are in part not very sharply marked off, extending as far aa 

 the extremity of the posterior segment of the body. The whole 

 nervous system lies in the body-cavity, not imbedded in the body- 

 wall, as is the case in Ctenodrilus and Parthenope. 



So much for the preliminary characterization of this interesting 

 Chsetopod, which measures a few millimetres in length. I name it 

 Vetrovcrmis hijaJinns, nov. gen. et spec. As a locality of consider- 

 able elevation I may cite the lake of St. Moritz in the Upper Enga- 

 dine. — Zoologischer Anzeiger, no. 270, January 23, 1888, p. 48. 



On Psorospcrmium Haeckelii. 

 15y Dr. (JiTO Zachakias. 



Years ago (1855) Hackel, during a microscopic examination of 

 the tissues of the freshwater crayfish, discovered a peculiar parasite, 

 which does not appear to have been since frequently observed. 

 Grobben * (1877) again found it in the connective parts of the testis 

 in Astacus, and recently (1883) Hilgendorf f also observed it, espe- 

 cially in the vicinity of the thoracic chain of ganglia in the crayfish. 

 " In order to fix the structure in question by a definite name " the 

 last-mentioned author has proposed the designation FsorosjpeivniiDu 

 ifcecl-elii. 



Last summer (1887) I frequently met with the sporozoon in 

 question during the investigation of Silesian crayfish, and I ascer- 

 tained its presence also in examples from Galicia (Tarnopol). It 

 must therefore be a generally distributed parasite, but one which 

 does no injury to its host. The specimens of Astacus examined by 

 me were apparently quite healthy. 



The organisms under consideration possess an elongated oval 

 form and are sharply marked oft' from the tissues of their host by a 

 firm cuticle. Their longitudinal diameter measures about O'lSO 

 millim., their greatest breadth only 0-040-0-05U millim. Their 

 thickness is also very small. They are flat, tongue-shaped structures, 

 which may be met with in many thousands in a single individual 

 crayfish. It is not impossible that when they increase to too great 

 an extent they may cause epidemics among the crayfish. At any 

 rate it will be advisable to examine (microscopically) from this 

 point of view the tissues of diseased Astaci. 



According to my obsei'vations Fsorospermium Hceclcelii occurs less 

 frequently in young than in old crayfish. I have thoroughly ex- 

 amined all the tissues of individuals two inches long, and found 

 nothing. When on the point of desisting from the microscopic 

 examination I remembered that the eyes of the animals had been 



* ' Beitr. zur Kenutn. d, miinul. Geschlechtsorg. der Decapoden,' &c., 

 1878. 



t Ber. Gesellsch. uaturf. Freunde iu Berlui, Sitz, am 20 Nov. 1883. 



