76 RICHARD EVANS. 



were in the last-mentioned embryo. The endodermal cells 

 are distinctly columnar and rather long, features which are 

 gradually becoming more marked stage by stage. In the 

 eleventh embryo found in the uterus the endoderm possesses 

 the same characteristics as in the last embryo, but all of 

 them are much more highly developed. The cells are longer 

 and possess more marked outlines, and the food-bodies are 

 larger and more numerous. In the twelfth embryo occurring 

 in the uterus all the features which characterised the eleventh 

 are present; but the cells are still longer, and the food-bodies 

 have increased both in size and number. In the last two 

 embryos the cavity of the gut is partially filled with a kind 

 of debris. The globules occurring in the endodermal cells 

 of the older embryos found in the uterus are undoubtedly 

 the same as those found in the same position in the adult. 



It will be noticed that there is in the above account of the 

 development of the endoderm in Eoperipatus no mention 

 of a histolytic process, such as has been described by Dr. 

 Willey in P. novse-britannias (7), If such a breaking 

 down of the endoderm took plate in Eoperipatus, it is 

 not likely that it would have been missed, as the nine 

 embryos whose endoderm has been described above repre- 

 sent all stages of development, ranging from an early 

 gastrula to an embryo coloured almost like the mother. As 

 far as P. novas-britanniae is concerned Dr. Willey seems 

 very decided; but when the subject is critically examined it 

 does not seem so certain that the process of histolysis de- 

 scribed by Dr. Willey does really take place in nature. In 

 the first place, his specimens were preserved in formal, 

 without opening them, consequently the preserving fluid had 

 to penetrate not only the body-wall of the mother, but also 

 that of an embryo almost ready for birth. To say the least 

 it is very doubtful whether formal is capable of doing this. 

 In the second place, the endodermal layer of the older 

 embryo found 'in the uterus should not be compared, as 

 regards difficulty of preservation, with ordinary tissue, such 

 as the coelomic end-sac of the renal organs, but with such 



