378 



KNOWLEDGE. 



September, 1910. 



small primordial chamber are known as the 

 inicrosplieric form or Form B. The microspheric 

 tvpe is always much less abundant than the megalo- 

 spheric. In Po/vs/o;Ht'//a cr/,s/)c7. according to Lister, 

 the proportions of the two forms are as thirty-four 



to one, but 



he thinks 

 it probable 





tI 



man}- small nuclei distributed throughout the bodv. 

 (Figure 2, A and B). 



The relationship of the megalospheric form to the 

 microspheric became apparent when the life-history 

 of the animal was worked out. The approach of the 

 reproductive phase, as seen in a li\ing microspheric 

 individual, was marked by a large increase in the 

 discharge of pseudopodia. The\' became so abundant 







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!:%>■:. 



.A. FiGU 



Stages in the reproduction of the micros 



B 



RE 3. 



pheric form of Polystiiiiiclla crispa. 





that the proportions ma}- var\- with the season. 



Lister's methods and results are to be found in 

 the papers referred to in the Bibliograph}- at the end 

 of our note. We present a brief summar\- duK-. 



Living specimens were 

 killed and fixed b\- means 



of a warm saturated solu- c 



tion of corrosive sublimate 

 and glacial acetic acid in 

 the proportions of four to 

 one. This had the effect 

 of rapidly dissolving the 



\ o e , 

 6 



'^€^6 



tA-<-, 



\1, 



as to form a halo round the shell (Figure 3, A). 

 This was at first clear protoplasm, but subsequently 

 the brown granular matter passed out of the shell 

 until all its protoplasm was outside, leaving the shell 



empt\- (Figure 3, B). After 

 ^ streaming movements in 



the extruded protoplasm, 

 it separated into spherical 

 n-iasses of equal size, each 

 surrounding a nucleus. 

 )herical 







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<: 

 c 



■1 J 



-!0 *a 





f 



\ 





calcareous shell while pre 



serving the protoplasm 



body as a perfect internal 



cast of the shell. All the 



bodies, irrespective of size 



or stages of growth were 



found to be separable into 



two groups, megalospheric 



and microspheric. In the 



megalospheric specimens 



the " retral processes " 



characteristic of the genus 



were obser\-ed in the 



chamber next to the 



megalosphere, but in the 



microspheric siiecimens 



the " retral processes " 



were not to be seen in any of the early con\-olutions. 



On staining the protoplasmic bodies with [)icro- 



carmine it was found that the megalospheric and 



microspheric forms were also sharph- contrasted 



in the number and character of their nuclei, the 



megalospheric form having but a single large 



nucleus while the microspheric forn-i possessed 







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P'lGURE 4 



A later stage in the reproduction of the same specimen 



showing the formation and separation of the young 



megalospheres. 



Each sptierical in ass 

 secreted a calcareous shell 

 with a single aperture 

 (Figure 3,0. The spheri- 

 cal masses, w-hich were of 

 identical size with the 

 prii-iiordial chambers of 

 megalospheric specimens, 

 then began to separate 

 and disperse (Figure 4), 

 and shortly after each one 

 formed a second chamber, 

 which possessed the 

 characteristic "retral pro- 

 cesses," and was recognis- 

 able as a young megalo- 

 spheric individual. The 

 whole process, from the 

 formation of the halo to 

 the disjiersal of the \-oung brood, occupied about 

 twelve hours. 



It was thus proved that a 1-1-iicrospheric adult 

 produced megalospheric children. Follow-ing up the 

 histor\- of these. Lister found that as the}' increased 

 in size and nun-iber of chambers the nucleus also 

 increased in size, and ni()\ed onward through the 



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