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THE AMERICAN NA TURALIST. [Vol. XXXVII. 



cells well filled with granular contents. There is no projection 

 of the entodermal axis into the hydranth cavity as we found in 

 Corymorpha. 



A number of sections of Titbularia larynx were examined for 

 further comparison. The structure of this species agrees in con- 

 siderable detail with that of T. couthouyi. 



Allman ('71, p. 205) describes a similar condition in Titbularia 

 indivisa. He says : " The stem of Tubularia indivisa presents 

 immediately within the perisarcal tube a continuous layer of 

 ectoderm enclosing the endoderm, which extends to the very 

 center of the stem and thus obliterates all trace of a central 

 somatic cavity. The place of the cavity however is supplied by 

 numerous canals which are excavated in the endoderm and take 

 a longitudinal course through the stem, occasionally communicat- 

 ing by lateral offsets with one another and finally all merging in 

 a common central cavity at the base of the hydranth." He 

 further states that the canals are of unequal size, " one of them 

 especially being in almost every instance considerably larger 

 than any of the others." L. Agassiz ('62) says that a similar 

 condition as to the size of the canals may sometimes be detected 

 in T. couthouyi, although I was unable in my observations to 

 perceive any appreciable difference in size. 



(b.) Papilliform processes. — The lower part of the stem of 

 Corymorpha is covered with numerous short conical papilla: 

 arranged in an irregular longitudinal series and apparently fol- 

 lowing the course of the canals. Lower down toward the base 

 of the stem these papillae increase in length and in many speci- 

 mens these small processes were seen in all stages varying from 

 very short blunt papillae above, to extremely elongate filaments 

 below. Immediately below these processes are found the numer- 

 ous filamentary rhizoids which cover the saccular portion of the 

 perisarc. The presence of these two structures at the base of 

 the stem and the apparent merging of the one into the other 

 naturally suggests the problem as to their relation and derivation. 

 Upon examination of transections of the stein in this region we 

 find that these papillae begin as simple outgrowths of the ecto- 

 derm. (Fig. 3.) At the same time the mesogloea directly under- 

 neath these outgrowths is seen to grow very much thinner, and 



