28 BULLETIN OF THE 



6. Formation of the Individual. 



Recent careful studies on the formation of the individual in other 

 Endoprocta, especially by Seeliger ('89"), render a detailed study of this 

 process less necessary. There are a few points concerning the physio- 

 logical rather more than the morphological features of this process which 

 I have attended to in this case in order to test certain conclusions which 

 I had arrived at from the study of the earliest stages of budding in 

 Ectoprocta. 



First, the budding regions are areas of cuboidal cells, with relatively 

 large nuclei and deeply staining plasma. Such a condition is found in 

 both the ectoderm and mesoderm of the proliferating region (Plate VI. 

 Figs. 50, 57). The relative enlargement of the ectodermal cells, and 

 at the same time a bending of the whole layer outward, give rise to 

 the first fundament of the new individual. The musculature of the 

 new individuals is certainly not derived directly from that of the old 

 stalk, for this takes no part in the outbending. Upon the apex of the 

 cylindrical protuberance thus formed the polypide is produced. The 

 dptails of this process I have not followed. 



Secondly, the position and time of origin of the buds arising from the 

 stalk are very definite. They make their appearance in a zone lying in 

 the lower part of the segment (Plate VI. Figs. 50, 58-60), and shortly 

 after the formation of the dissepiment which lies just below. 



One of the questions the re-examination of which most interested 

 me was that of the origin of the alimentary tract, since this is stated to 

 arise differently in Endoprocta and Ectoprocta. 



In an optical section of the whole bud (Plate VI. Fig. 53), it could 

 be seen that the atrium was connected with the young alimentary tract 

 at the oral end only. The same thing is shown in the series of trans- 

 vei'se sections, Figures 54-56, in which the distal (anal) part of the 

 atrial chamber is not confluent with the rudiment of the alimentary 

 tract which touches its floor. Figure 54, but the two organs are con- 

 fluent at the proximal (oral) part, Figure 56. Figure 52 is from an 

 optical longitudinal section of the bud shown in Figure 53, taken in a 

 plane perpendicular to that of Figure 53. Here the alimentary tract, s^ 

 (Fig. 52 ; ga. Fig. 53) is being constricted off from the atrium. 



Like the young bud, the growing tip of the stolon possesses an ecto- 

 derm consisting of large cuboidal cells (Plate VI. Fig. 57). The mesen- 

 chymatous tissue also consists of thickly crowded, undifferentiated, and 

 deeply staining cells (Figures 51, 57). 



