538 MR. A. LISTER ON THE DIVISION OF 



but showed in considerable abundance when the elaters were 

 forming (PL XXXV. fig. 3). They were, for the most part, 

 more deeply stained than the normal nuclei and resembled oil- 

 globules enclosed in vacuoles ; intermediate forms showing more 

 or less of reticulated structure were found between these and 

 the well-formed nuclei. At the stage when the spindle occurred 

 they were more faintly stained, and when the spores appeared 

 they were often difficult to detect, although most of the spores 

 contained one or two of them (PI. XXXV. fig. 8). In Physarum 

 leucophaum they were more striking than in the last-named 

 species. In the first stage, when the sporangia were just rising, 

 they were conspicuous by their dark staining, the absence of 

 reticulated structure, and by appearing in pairs, often apparently 

 adhering, the couples being surrounded by a hyaline envelope. 

 Tour hours later they were still more numerous, of the same 

 character as in the former staining, and with the couples in great 

 numbers. Two hours later again, when the nuclear halves had 

 divided, they were no longer in couples, but so numerous that 30 

 could be counted in one field of the ^ ob. gl. In another hour 

 the spores had formed and a large number of them contained one 

 or more of these nuclear bodies enclosed in a vacuole as deeply 

 stained as the true nucleus. 



These observations may not be of much value, but the objects 

 are so striking that they can hardly be passed over without notice. 



The experiments above described were made with three species 

 of Trichia, one of Comatricha^oxxe of Physarum, one of Badhamia, 

 and one of Arcyria, representing genera of widely differing 

 characters. They give essentially the same results and afford a 

 definite confirmation to Strasburger's surmise that division by 

 karyokinesis in the sporangia of Mycetozoa is only found imme- 

 diately before the formation of spores. They also show that in 

 the cases in which the stainings have been carefully timed this 

 division occurs but once, and within an hour from the period 

 when the young spores make their appearance. 



"We have now to consider the change which takes place in the 

 nuclei of the swarm-cells when division occurs in those bodies. 



I had by me a specimen of Reticularia Lycoperdon gathered in 

 May 1890. Experience had shown that it is a species whose 

 spores germinate rapidly and with great regularity, but as the spe- 

 cimen had been preserved in a dry cupboard in which naphthalin 

 had been freely scattered from time to time, it seemed doubtful 



