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LEWIS R. GARY. 



had undergone laceration was very high. In fact this form of 

 reproduction was much more frequent in the ^last-mentioned 

 instance on the government jetties at Cameron, La., than in 

 the case of the same species from which the records were made 

 at Beaufort. 



INTERNAL CHANGES DURING LACERATION. 

 Under this head will be discussed the following topics: 

 (a) The formation of the stomodeum. 

 (&) The development of the mesenteries. 



(c) The development of the mesenteric filaments and acontia. 

 (J) General histological changes in the tissues during develop- 

 ment. 



(a) The Formation of the Stomodeum. 



As mentioned previously in the general account of the process 

 of laceration, the first noticeable change in the appearance of 

 a laceration piece after its separation from the parent consists 

 in the rolling in of the edges of the torn side of the fragment, 

 so that from the first the opening into the cavity of the fragment 

 is lined for some distance with ectoderm (Fig. 7, PI. II.). At 

 first the ectoderm extends forward for only a short distance on 

 the upper side of the opening, while on the lower side the inrolling 

 has progressed considerably farther. 



In a section through a stage such as is shown in Fig. 2, PI. I., 

 the stomodeum has the appearance such as is shown in Fig. 8, 

 PI. II. Here the free edges about the orifice of the fragment 

 have become thinner, the mesoglea is reduced to a thin sheet 

 of tissue and the cavity of the stomodeum has become vertical 

 instead of nearly horizontal as at first. At the lower, free, border 

 of the stomodeum the ectoderm has become turned outward 

 and extends around the border of the endoderm onto the internal 

 wall of the stomodeum. 



