( 220 ) 



rows (the same process was deseribed by Godlkwski foi' llie stiiped 

 muscle fd)res of the body muscles) and in this mauuei- the delicate 

 primitive histological myofdirillae are formed. In these originally 

 homogeneous fibrillae durijig the course of development two elements 

 appear, staining differently with irondiaematoxylin and eosin, the 

 first sign of cross-striation, of the anisotropous and isotropous discs. 

 The later stages of development and the appearance of the "Sclialt- 

 stCicke" were not studied by Godlkwski. 



An essentially similar view has suice been advocated by M.aiukau ^) 

 (1902). In a series of brief papers tins author described Ihe continuity 

 of the lieai't muscle fibres in mammals, birds and lower vertebrates, 

 and accepted in the main Hkidknhain's snggesliou of the funetion of 

 the "Schaltstiicke*' in the adult and llie still gi-owing heart. 



Iji teleosts — I refer especially to the eggs of the Aliiraenoïdae, 

 Avhich j)rovided me chiefly \\ itii the materials for the study of the 

 processes 1 am a'hout to desc-ril>e here — the heart muscle cells 

 are deri\ed fr(»m the cells of the mediati portion of the walls of 

 the jiericardial caxily, whieli, as i.s the case in all ananniia, grow 

 from either side underneath the entoderuial tube and fuse with each 

 other in the median line, so that a tul»e is h)i-metl between I hem, 

 which opens at one end into the yolk-sac, at thr other end inio the 

 arterial ves.sels, formed at the same time (ostium v(Miosum and ostium 

 arteriosum). Inside of this tube the endothelium of the heart is formed 

 out of cells of the "niasses intermédiaires" of the mesoderm of the 

 head and parllv out of cells which migrate from the region of the 

 tail-knob towards the heart, and lay themselves against the myocard 

 there where the heart tube op(Mis iuio the yolk-sac. 



In fig. 1 is reproduced a longitudinal section through the region 

 of the heart of an endiryo of Muraena X". 1 with 38 pairs of 

 muscle segments, which illustrates these features clearly. < )n the left 

 side of the dra\viiig the rostral end of the chorda is seen, and 

 beneath the chorda the entoderm, which shows the widening of 

 the oesophagus corresponding with the i)reopercular apertures, the 

 primary gill-clefts. Between the entoderm ami the |)eriblast the 

 heart is seen, atid at the \enous end of tiie heart tube lies a 

 cluster of loose separate cells, ^vhich Iw their peculiar form and 

 by the protoplasmic processes with which they (the greater part in 

 the following sections), unite with the endothelium of the heart, a[>pear 

 as cells which aid to luiild u\) the endocard. The history of the genesis 

 of the endocard however \vc \vill drop for the jtresent, the repro- 



1) G. R. de la Soc. de Biologie, T. öi, pag. 714—710, 9Sl — 984, 14S.5 — 1487; 11)02. 



