82 RECORD OF CURRENT RESEARCHES RELATING TO 



Vermes. 



Development of the Heart of Criodrilus. * — Dr. F. Vejdovsby 

 has published a preliminary notice on this subject, of which he gave 

 an account to the Eoyal Bohemian Society of Sciences on July 4th, 

 1879. He finds that the heart of Criodrilus commences from two 

 completely separated rudiments ; these gradually approximate on the 

 cardiac side of the enteron until they become completely one, and 

 form an unpaired dorsal vessel or heart. Although these rudi- 

 ments do, in their primitive characters, resemble the lateral vessels, 

 there is, later on, developed in the neighbourhood of each half a 

 layer which consists of transverse and of longitudinal muscles; 

 this layer becomes covered by larger peritoneal cells, which are 

 subsequently modified into the colossal peritoneal (or " chloragogal ") 

 cells. Kowalevsky has already shown that in Lumbricus the heart 

 has a similar origin ; and the supposition, justified by these observa- 

 tions, that in the Annelides the heart is always thus developed, is 

 supported not inconsiderably by the observation of Quatrefages, who 

 has shown that in the Hermellidas there are in the posterior region 

 two dorsal vessels, which only fuse into an unpaired heart in the 

 thorax. These facts bear, further, on the relationship between the 

 Annelides on the one hand, and the Arthropoda and Vertebra ta on 

 the other. Claus has shown that in Apus the dorsal vessel is primi- 

 tively formed of two symmetrical halves and Metschnikoff has esta- 

 blished the same relation in Geophilus ; while Hensen, Kolliker, and 

 Gasser report a similar mode of development for the vertebrate heart. 

 The very first stages of development were not observed ; but in a 

 section made across the anal segment (which in Criodrilus is not 

 terminal) the author observed two sets of vessels, one above and one 

 below the ventral ganglionic cord. The trunks which arise from the 

 upper pair, which lie at the sides of the coelom, anastomose with the 

 loops of the lower one, and also give off" a large number of lateral 

 capillaries ; the perivisceral loops are also formed by the upper pair, 

 while on either side of the anal groove there is a large vessel, with 

 which they communicate. In other sections the two vessels were 

 observed to lie in the cardiac half of the coelom, although not above 

 the intestine ; further on the two vessels begin to approximate, though 

 they are separated from one another by the paired muscular bands, 

 which attach the intestine to the body-wall. Yet again these bands 

 become single, and the dorsal vessels lose their simple structure, 

 while they become surrounded by a muscular layer and by a peritoneal 

 investment ; in the next stage the vessels lie close to one another, 

 and the muscles of attachment are inserted into the jieritoneal coating. 

 The two vessels then become completely united. The heart of Criodrilus 

 is stated to be best developed in the median segment of the trunk. 



Typhloscolex Miilleri W. Busch.t — This pelagic Annelide is 

 studied by Professor E. Greeflf, in an appendix to his paper, already 

 reported. J 



* SB. Bohm. Gesell. Wiss., 4th July, 1879 (separate copy). 



t 'Zeitsch. wiss. Zool..' xxxii. (1879) p. c,(\\. 



X Tliis Journal, ii. (1879) p. 888. 



