LIVING CONNECTIVE TISSUE CELLS 133 



selects the interval between the jointed rays the primitive actino- 

 trichia are thereby excluded. 



In such portions of the caudal fins of 6 mm. embryos, and in 

 equivalent places in later stages, are typical connective tissue 

 fibers mostly occurring as coarse longitudinal bundles with fine 

 oblique anastomoses. Single fibers occur in the intervals of the 

 coarser bundles. It is along these fibers and fiber bundles that 

 the stellate and spindle cells are disposed. These cells are readily 

 seen in the living fish, though the ease of observation is subject 

 to much variation in different individuals and to a less extent in 

 different portions of the same embryo. 



My observations were made on living embryos immersed in sea 

 water, some with, some without the addition of chlorotone. In 

 some cases a few drops of a saturated solution of Bismark brown 

 were added to the sea water in which the fish was kept, the effect 

 of which after a time was to slightly increase the color contrast 

 between the connective tissue cells and surrounding structures. 

 The stain seemed almost inocuous, for fish could be kept in it 

 for several days without apparent effect on their vitality. Many 

 of the fish thus examined were later killed, and the fins stained 

 and mounted in toto, or sectioned. The various cell types seen 

 in life were readily recognizable in corresponding locations in the 

 stained preparations. 



It is in life difficult or impossible to distinguish between the 

 spindle and lamellar types, though in 'fixed' tissue they may be 

 morphologically distinct. In the living animal one can see a 

 stellate or a spindle cell elongate, approach and flatten itself 

 against a connective tissue fiber or fiber bundle, becoming some- 

 times so attenuated as to be scarcely distinguishable from the 

 fiber against which it lies; it may at any time acquire increased 

 thickness. Such a relation to a connective tissue fiber is shown 

 by the cell b in fig. 2. The relationship is again exhibited by the 

 two cells shown in fig. 3, one of which a, approached a small 

 fiber bundle, became flattened against it, then rotated to the oppo- 

 site side of the fiber at 9.30 a.m., and later freed itself from the 

 contact. Its locomotion can be observed in relation to the chro- 

 matophore (ch) which served as a fairly fixed point. Similar 



