330 The Development of the Connective Tissues 



front of the brain the exoplasm has increased markedly in quantity, by 

 an addition to it from the mesenchyme cells at the growing point as 

 well as by a multiplication of the cells of the finished syncytium. The 

 same is true of the syncytium on the ventral side of the head. In the 

 tail the connective-tissue syncytium forms a very dense network of 

 exoplasm with nuclei and a small amount of endoplasm lying upon, or 

 imbedded within, some of the nodal points. The endoplasm about the 

 nuclei form stellate bodies with their points running out into the 

 general mass of exoplasm. Minute pigment granules, often in rows, 

 are distributed throughout the syncytium. 



In general we have here a stage similar to that described by Flem- 

 ming and by Spuler, and what I have stated above confirms' the work 

 of these investigators, though it formulates it somewhat differently. 



The connective-tissue syncytium is practically complete in embryos 

 6 mm. long. In its further development it spreads and enlarges to 

 form the general framework of the body. From now on there differ- 

 entiate from it, with the exception of the chorda, the permanent con- 

 nective tissues of the body, i. e., the skeleton, ligaments, tendons, true 

 skin, etc. 



Before discussing these tissues I shall describe the general arrange- 

 ment of the syncytium in a tadpole 9 mm. long after the cartilages are 

 beginning to form. In this embryo the syncytium around the anterior 

 end of the chorda is again fully developed, with a difference, however, 

 in the shape of the nuclei and endoplasm around them (Fig. 4). They 

 are now spindle-shaped, lie upon and are connected with the exoplasm 

 of the syncytium. In the course of time the nucleus and its endoplasm 

 separates itself from the exoplasm of the syncytium, which is gradually 

 converted into connective-tissue fibrils. The syncytium in front of the 

 brain of the embryo is formed of bundles of anastomosing exoplasm 

 with nuclei at some of the nodal points (Fig. 5). Each nucleus has a 

 small quantity of endoplasm around it, forming a spindle-shaped mass 

 which runs out into points to be lost in the exoplasm of the syncytium. 

 In specimens of this kind it is easy to view these cells with their endo- 

 plasm as the connective-tissue cells and the exoplasm of the syncytium 

 as the intercellular substance were not the development of the syncy- 

 tium taken into consideration. Within the syncytium certain of the 

 fibrils are more sharply defined than the rest, which indicates that in ad- 

 dition to the shifting of the nucleus and its envelope of endoplasm there 

 is already some differentiation Avithin the exoplasm. The syncytium 

 in the ventral side of the head is much like that just described. As 

 this is followed towards the tail there is a gradual transformation of 



