97 



ding to the general opinion by accumulation or transmutation of 

 waste-products. The origin and fate of these protein-crystalloids 

 has been studied in detail by List 81). They are very regular 

 crystals, generally hexaeders or rhomboeders, which show the 

 typical reactions with J in KJ, with eosin, Millon's reagent 

 and picric acid. They are found in the nuclei of the corpuscles, 

 also in those of the cells of the middle-gut, as in many other 

 cases (see ') ), and occur especially in the „amibocytes incolores" 

 of C u e n o t. In the middle-gut of Tenebrio they are found not 

 only in the nucleus, but also in special inclusions of the cell-body, 

 reminding one of the aleuron-grains in plants and even free in the 

 cell protoplasm. More than one crystal is never found in our 

 urchins, they are preceded by small, round bodies (protein vacuo- 

 les ?) which later on unite to form larger ones. Whether or not 

 these crystalloids actually are reserves, is not clear from this 

 research; it is the opinion of the author that „nach den am 

 lebenden und conservierten Materiale gemachten Beobachtungen, 

 es sehr wahrscheinlich ist, dasz die Krystalloide sich schliesslich 

 in Pigmentkorner umwandeln". 



All the evidence collected in this chapter shows clearly that 

 large amounts of reserves are not present in our group. Lack of 

 time has prevented me from investigating this point more in detail. 



26. GENERAL METABOLISM. 



Though I do not have to oifer any experiments of my own 

 in this chapter, it has been added because as I said in the 

 introduction, this paper aims to give not only original work, 

 but also a review of the literature on the subject. Moreover 

 some critical remarks must be made on one of the most para- 

 doxical modern theories on nutrition, on Putter's theory of 

 the nutrition of marine animals. 



Two papers in which an attempt is made to study the 

 metabolism of the Echinoderms have come to my attention, 

 one by Cohnheim 17) and one by P titter 105). Both con- 

 cern themselves with dendrochirote Holothurians, Cohnheim 

 works on Holothuria tubulosa, Putter on Cucumaria grubei. 



Cohnheim's paper is of a very preUminary nature, in 

 fact, it does not contain much more than a few experiments 

 on the CO2 cutput. His experimental procedure is of the sim- 

 plest kind; he puts some animals in a stoppered bottle having 

 two outlets. O2, purified by NaOH, is bubbled through the 

 apparatus. The outcoming air is led through baryta and the 

 amount of CO2 produced estimated by titration. 



The output per K.G. hour appears to be somewhere in the 

 neighborhood of 0.147 gr. In the case of Ophioderma longi- 



1) See e.g. Joh. Frenzel. Berl. Ent. Ztg. Bd. 26. 1882. p. 267-361. 

 C. Ren gel. Zs. wiss. Zool. Bd. 28. 1896. p. 1-60. 

 P. Mangazzini. Mitt. Zool. Stat. Ncapel. Bd. 9. 1889. p. 1-60. 



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