THÉEL, THE AMOEBOCYTES BY ECHINODERMS. 5 



of coelomic fluid, one becomes struck with wonder, traces of resem- 

 blance beiiig scarcely discernible. Shape, size and structure are dis- 

 similar. In vain, I have striven to find any other acceptable reason 

 for this change of the general appearance than that tho peripheral 

 ectoplasm of living leucocytes is very difficult to see, and therefore 

 escapes tlie observance ' of the investigator, this part of the protoplasm 

 being visible first after fixation and staining. » 



Page 20. »B ut if it be taken for granted that plasma- amoebo- 

 cytes of various shape and different in several respects pass their life 

 within the perivisceral cavity of the echinids, it is a fact as well that 

 an abundance of priniitive, globular, amoeboid corpuscles courses 

 there, presenting themselves in the preparations as discoidal flatte- 

 ned cells of varying circumference, and with or without peripheral pro- 

 trusions. » 



Page 21. »It is conceivable, that such primitive cells, like the 

 mesenchyme cells [of the larvae], are in possession of a tendency or 

 potency to perform such thorough alterations, that they, influenced 

 by different conditions, acquire the faculty of changing form and 

 structure and, besides, of being able to perform different functions. » 



Pages 21-22. »AVhere are such essential conditions met with, 

 which may be able to exercise such an influence that they call forth 

 these latent forces and lively activity of the coelomic amoebocytes? 

 For the present, a satisfying answer can scarcely be given. However, 

 it may be presumed that the character of the surrounding medium may 

 play an important part in that, and above all movement and relative 

 stillness, the former preventing, the latter forwarding the process of 

 transmutation. If, for inst., an amoebocyte leaves the coelomic cav- 

 ity in order to immigrate into the tissues of the body-wall, it must 

 necessarily undergo certain changes of form. When a cell passes över 

 from a passive drift to an active motion, its primitive globular confi- 

 guration must be exchanged for another and accommodated to cree- 

 ping about. Within the tissues and undisturbed of coelomic currents, 

 the amoebocyte has a favourable opportunity of transmutation and 

 of fusing together with neighbouring leucocytes, so as to form there 

 plasmodia or reticular and fibrous syncytia. » 



Pages 22-23. »In this connection I will pay ätten tion to the 

 question, how the amoebocytes behave within the coelomic cavity 

 after that they there have been subject to more thorough metamor- 

 phoses, or have fused together in order to result in the formation of 

 syncytia [ — ef. the plates in my papers on Äst. rub. and Parecli. mil.]. 

 Is it possible, that the bipolär or multipolar cells with their long pseudo- 

 podial protrusions could be able to resumé their original primitive 

 configuration, or that the syncytia or plasmodia could break up into 

 their primordial components? Though, in want of sufficient evidence, 

 I cannot believe this taking place, at least not in most instances. Ne- 

 vertheless, I alluded to the possibility that the syncytial woolly dus- 

 ters in the coelomic fluid of Ästerias riibens may be able of breaking 

 up into their components, in order to result in the amoebocytes be- 

 coming free again. » 



