

TI M 





t ') 



unfortunately, unsuccessful .nul th< account which follows is based entirely upon series prepared 



individuals measuring about 3.0 mm. I h<- general arrangement of the mesenteries is shown 



in t: mpanying textfigure \'I11, from which it will I"- seen that in addition to the eight 



protocnemes, tuur deuterocnemes were present on either side, a some- 



wh.it smaller rjumber than that OCCurring in individuals of .tliiiiit the 

 same size "t P. (equator ialis. The firsl couple "f protocnemes were. 

 as usual, short and entirely destitute of mesenterial filaments. The 

 cond couple were, on the other hand, the longest of all the m< 

 •.eiie-,. tor ;i consideratie distance below their separation from the 

 stomatodaeum they possessed no filaments, hut toward the aboral 

 extremity <>f each a filament appeared and it terminated after a short 

 course in a well developed acontium. The third couple po 

 filaments throughout almost their entire length, these filaments branching 



of the mcsenleric> of a iini of 



in part of their course. The fourth couple resembled the second so 



vin. 



g the a 

 tentene 



far as the arrangement of the filaments was concerned, except that 

 filaments were even shorter and the acontia smaller. 



The t'irst and third deuterocnemes on either side resembled the third protocnemes in 



structure, and the second deuterocnemes resembled the fourth protocneme, except that they 



-s no acontia: the fourth couple of deuterocnemes were as vet unprovided with filaments. 



From the second protocnemes onward the lengths of the mesenteries diminished ^radually, 



quartette arrangement of the deuterocnemes bein^ indicated only by the structure of their 



filaments. It seems probable, however, that an alternatin^ difference of the quartette mesenteries 



will appear with further development, since it is already clearly indicated in the figure of /'. 



aquatorialis yiven by van Beneden. It is to be noted that in that form as well as in pilula, 



-econd protocnemes are the longest of all the mesenteries and this fact, together with the 



occurrence of acontia upon them in pilula, renders it ])robable that they will become the 



telocnemes. The presence of acontia in pilula is in marked contrast to their absence in the 



somewhat more advanced individuals of aquatorialis. 



.\s regards the finer structure it may be stated that the mesogloea is thin throughout, 



ially so in the mesenteries where it forms a sheet of extreme tenuity. The ectoderm 



lins numerous gland cells and at the aboral pole nematocysts were quite abundant, although 



wen- r r other portions of the column. The ectodermal musculature was well devel- 



much ni' than in van Beneden's examples of aquatorialis, the muscle cells being 



arranged "ii quite well developed muscle processes. The stomatodaeum presented the same 



■al histological characters as in other forms and possesses a well marked siphonoglyph. 



No reproductn were present in any of the mesenteries. 



34 



