10 ARKIV FÖR ZOOLOGI. BAND 13. N:0 25. 



present themselves under almost the same various forms as 

 those seen in Asterias rubens and Parechinus oniliaris. Thus 

 we meet with discoidal cells devoid of pseudopodial protrusions 

 side by side wdth f an-shaped cells prolonged into a long, narrow 

 handle, elongated thread-like cells, and more or less exjoanded 

 ones protruding a number of pseudopodia, which often reach 

 a considerable length and meet those of neighbouring cells 

 in order to fuse togetlier with them, and to form thin syncytia. 



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Text-figure 2. Two plasma-amoebocytes and six dubious spermatozoa- 

 like corpuscles from the coelomic fluid of Thyone fusus, fixed, stained 

 and mounted in balsam, The plasma cells having evidently devoured 

 »amoebocj^tes with spherules». 



Thyone fusus. 



In preparations of the coelomic corpuscles, fixed immedi- 

 ately after removal from the animal, one finds again the same 

 types of isolated amoebocytes and unions of them as in the 

 preceding species. The syncytia are, as a rule, small and thin, 

 but once (19^76 19) I was successful in obtaining a preparation 

 presenting an extensive net-work, which covered an area on the 

 glass slide of 20X25 mm. This syncytial net-work bears the 

 closest resemblance to the figures drawn on the plates 3 and 4 

 in my paper on Asterias rubens. It is w^orthy of notice that the 

 coelomic corpuscles were fixed 17 hours after the removal 

 from the animal. That is the only time, that I have seen such 

 an extensive syncytium in a holothurid. 



In specimens kept in aquaria and bereft of food, it is 

 not rare to see true plasma-amoebocytes encircling one or two 



