EFFECTS ON THE HIGHER INVERTEBRATES 43 



passages later undergo progressive reduction. The testes are quite resistant, 

 but in six months of fasting are reduced greatly in size and consist of small 

 groups of three to five cells each, scattered through the "parenchyma." Even 

 the spermatogonia may finally undergo necrosis and chromatolysis. Schultz 

 (like Lillie) compared the reduction process to a reversal of the normal 

 development, so that inanition may lead to a rejuvenation of the organism. 

 He also considered the order of sequence in the loss of organs as a useful adapta- 

 tion, the less important organs being sacrificed first, the most essential (and least 

 differentiated) cells persisting longest. 



Stoppenbrink ('05) made a most careful and thorough study of the changes 

 during inanition, chiefly in Planaria gonocephala, but also in Planaria alpina, 

 Dendrocoelum lacteum and Polycelis nigra. The extreme limit of duration found 

 was fourteen months in Planaria gonocephala and ten months in Planaria alpina. 

 The marked reduction in body size corresponds in general to that noted by pre- 

 vious investigators. There is also a marked change in the body form, the 

 relatively large head and short postpharyngeal portion of the body resulting 

 from unequal reduction in the different regions. 



The reduction process in the various organs was found in general somewhat 

 similar to that described by Schultz in Planaria lactea, but certain differences or 

 additional features were noted. In the reduction of the intestine, no scattering 

 of the epithelium in the mesenchyme was found (P. gonocephala, D. lacteum). 

 The vitelline glands ("Dotterstocke"), in which the fat deposits of the body are 

 concentrated, do not lose this fat quickly during starvation, as might be expected, 

 but retain it tenaciously, until the organ has undergone extensive retrogressive 

 changes, with cellular necrobiosis and syncytial degeneration. The sexual duct 

 system degenerates much later than the vitelline glands. The ovary and testes 

 are the most resistant of all, although the sex-cells undergo regressive changes. 

 Stoppenbrink summarizes his results as follows: 



"Wahrend die Grossenreduktion in einem gleichmassigen Kleinerwerden 

 samtlicher Zellen eine ausreichende und einfache Erklarung finden wiirde, 

 deutet die Veranderung der Korperform auf anderweitige, gleichzeitig mitwirk- 

 ende Ursachen hin. Diese Ursachen sind darin zu erblicken, dass eine 

 ungleiche Beeinflussung der verschiedenen Gewebe stattgefunden hat, indem 

 die entbehrlicheren Organe zugrunde gingen, um mit ihrem S toff material die 

 Organe vor dem Untergang zu bewahren, die fur das Tier unumganglich not- 

 wendig sind. Eine stattfindende Nekrobiose lasst sich nur dort feststellen, 

 wo untergehende Zellen in grosserer Menge beieinander angetroffen werden. 



"Im Nervensystem, Darm, Exkretionsgefasssystem, Parenchym, Hauttnuskel- 

 schlauch und Korperepithel trat ein gleichzeitig stattfindender Zerfall von 

 Zellen in grosserem Umfange nicht ein. Dagegen liessen sich Degenerations- 

 prozesse deutlich im Bereiche der Geschlechtsorgane beobachten, die zu einer 

 totalen Riickbildung dieses Organsystems fiihrten. 



"Dieses Prozess erfolgte in der Weise, dass zuerst die Dotterstocke 

 angegriffen wurden, im spateren Verlauf der Begattungsapparat und zuletzt die 

 Hoden und Ovarien. Dabei trat eine Phagocytose nicht ein, die Elemente 

 zerfielen an Ort und S telle und wurden resorbiert. 



