Apkil 20, 1906.] 



SCIENCE. 



633 



SPECIAL ARTICLES. 



EPITHELIAL DEGENERATION, REGENERATION AND 



SECRETION IN THE MID-INTESTINE OF 



COLLEMBOLA. 



In Collembola, a degeneration of the inner 

 half of the epithelial wall of the mid-intestine 

 occurs in connection with each ecdysis. The 

 cells of the mid-intestine become confluent and 

 important changes of alveolation ensue ; nearly 

 half the nuclei migrate toward the intima, 

 while the rest of the nuclei remain near the 

 basement membrane; a wall now forms be- 

 tween the two sets of nuclei, dividing the 

 epithelium into two concentric layers. The 

 inner of these two layers degenerates; the 

 cytoplasmic reticulum disintegrates; the 

 nuclear membranes disappear and the chro- 

 matin granules become scattered, but remain 

 intact ; much of the fluid substance is resorbed 

 into the remaining layer of cells. The dis- 

 organized epithelium, surrounded by a peri- 

 trophic membrane, is expelled through the 

 rectum shortly after the external moult. 



The process is an excretory one. By this 

 means, the rapidly accumulating concretions 

 of sodic urate are removed from the cells of 

 the mid-intestine, as are also, but incidentally, 

 certain unicellular parasites (GregarinidEe). 



The nuclei lost by degeneration are replaced 

 by the mitotic division of the remaining nuclei 

 — this occurring before the inner portion of 

 the epithelium is cast off. 



The peritrophic membrane, which always 

 envelopes a food-mass, is formed by the split- 

 ting of the intima, and is, therefore, a secre- 

 tion from the epithelium of the mid-intestine. 

 The wall that divides the originally single 

 layer of cells into two layers, splits into two 

 membranes, one of which surrounds the degen- 

 erating epithelium as a peritrophic mem- 

 brane, while the other forms the new intima 

 of the -mid-intestine. 



The formation of new cells takes place 

 throughout the epithelium by mitosis; this 

 regeneration does not occur from local centers, 

 or ' crypts,' as it does in other insects ; f urther- 

 niore, no amitotic divisions are found at any 

 time. 



Secretion is performed (1) by the general 



epithelium of the mid-intestine ; (2) by special 

 clear cells in the middle region of the mid- 

 intestine; (3) by specialized cells in the pos- 

 terior region; these last give off proliferations 

 into the lumen, which become constricted off, 

 as free, rounded, cytoplasmic vesicles, which 

 break down in the alimentary canal and mingle 

 their contents with the food (much as in other 

 insects). 



The novel role of the mid-intestine as an 

 organ of excretion is correlated with the ab- 

 sence of Malpighian tubes in Collembola. 



Justus W. Folsom, 

 MiKiAM U. Welles. 

 Entomological Laboratory, 

 University of Illinois. 



earthquakes RECORDED AT CHELTENHAM MAG- 

 NETIC observatory JANUARY 24-31, 1906.1 



1. January 24: 



North-South East-West 



Component. Component. 



Beginning 2 h. 04 m. 10 3. 2 h. 04 m. 28 s. 



Beginning principal portion 2 04 10 2 04 28 



End principal portion 2 08 18 2 08 28 



End 2 83 56 2 29 48 



Maximum amplitude 2,0 mm, at 1.8 mm, at 



2 h. 06 m. 32 s, 2 h, 06 m. 08 s. 

 Average period of waves : 



Maximum 11.0 a. 10.8 s. 



End 7.2 8.0 



2. January 24: 



Beginning 2 h. 42 m. 12 s. 2 h. 42 m, 38 s. 



Beginning principal portion 2 43 20 2 43 03 



End principal portion 2 46 12 2 45 34 



End 2 52 50 2 51 39 



Maximum amplitude 1.5 mm. at 2.2 mm. at 



2 h. 44 m. 14 3. 2 h. 44 m. 48 3. 

 Average period of waves : 



Maximum 10.5 s. 12.3 b. 



End 7.2 8.6 



3. January 24: 



Beginning 16 h. 58 m. 50 s. 16 h. 58 m. 20 >. 



Beginning principal portion 16 59 20 16 59 20 

 End principal portion 17 02 60 17 03 30 



End 17 10 50 17 08 30 



Maximum amplitude 1.0 mm. at 0.6 mm. at 



17 h. 01 m. 34 s. 17 h. 00 m. 25 s. 

 Average period of waves : 



Maximum 11.6 s. 9.2 g. 



Beg. prin. portion 9.1 — 



End prin. portion 8.8 7.1 



' Communicated by the superintendent of the 

 Coast and Geodetic Survey, Mr. O. H. Tittmann. 

 The observatory is situated at Cheltenham, Md., 

 in latitude 38° 44'.0 N. and longitude 76° 50'.5 

 west of Greenwich. The times recorded are 



