344 



SCIENCE 



[N. S. Vol. SLVI. No. 1188 



and wasps was essentially a blind sac.'' The 

 subsequent establishment of communication 

 between the mid and hind-intestine in the 

 larvae of various members of the Hymenoptera 

 was long since noted and has been studied in 

 detail by Eengel.^ The relation of the Mal- 

 pighian tubules to the hind-intestine in the 

 Hymenoptera has, on the other hand, been 

 strangely neglected, being mentioned only in- 

 cidentally or completely ignored. For example, 

 both Anglas^ and Eengel merely state that in 

 the late larva or semipupa of the honeybee the 

 Malpighian tubules open into the hind-intes- 

 tine, and ignore the earlier stages. Kara- 

 waiew* and Perez' describe the Malpighian 

 tubules in the ant larva as opening into the 

 hind-intestine. This condition, however, does 

 not obtain in case of the feeding larva of the 

 honeybee, the central (caudal) ends of the tu- 

 bules being blind from the time of hatching 

 up to the sealing of the cell. The relation of 

 the tubules to the hind- and mid-intestine dur- 

 ing the feeding period is briefly as follows: 

 The posterior end or fundus of the mid-intes- 

 tine is, as already stated, completely closed, 

 the epithelium being continuous here. The 

 cephalic end of the hind-intestine is enlarged 

 and the motith of this enlargement closed by 

 a thin diaphragm-like layer of cells contin- 

 nous marginally with the wall of the hind-in- 

 testine The central part of this diaphragm- 

 like structure is closely applied to the external 

 surface of the fundus of the mid-intestine 

 which is here devoid of a muscular coat. The 



1 Dutrochet, E. J. H., ' ' MSmoire sur les m6ta- 

 morphoBes du canal alimeiitaire chez les Inseetes, ' ' 

 Jour, de Phys., LXXXVI., 1818. 



2 Eengel, C, ' ' Uber den Zusammenhang von 

 Mitteldarm und Enddarm bei den Larven der 

 aculeaten Hymenopteren, " Zeit. wiss. Zool., 

 LXXV., 1902. 



3 Anglas, M. J., ' ' Observations sur les meta- 

 morphoses internes de la Guepe et de I'Abeille, " 

 Bull. Sci. France et Belg., XXXIV., 1901. 



< Karawaiew, W., ' ' Die nachembryonale Ent- 

 wicklung von Lasius flavus," Zeit. wiss. Zool., 

 LXXV., 1898. 



Perez, Ch., ' ' Contribution a 1 '6tude des meta- 

 morphoses," Bull. Sci. France et Belg., XXXVII., 

 1903. 



pointed central blind ends of the four Mal- 

 pighian tubules are inserted between these 

 two layers, two on each side, but their tips do 

 not extend quite to the center of the area of 

 attachment of the mid- and hind-intestines. 



In the newly hatched larva the Malpighian 

 tubules are slender tubes, and pursue a wind- 

 ing course from their point of attachment up 

 to the second or third thoracic segment, lying 

 between the capacious mid-intestine and the 

 body wall. Their lumen is minute, the walls 

 being relatively very thick and composed of 

 cells whose depth and breadth are approxi- 

 mately equal. In the mature larva on the other 

 hand the Malpighian tubules are relatively vo- 

 luminous, attaining, near their posterior ends, 

 a diameter greater than that of the hind-in- 

 testine. The posterior or central ends them- 

 selves, however, always remain of small di- 

 ameter. Sections through the tubules at this 

 stage show that the walls are extremely thin 

 and composed of flat cells. In fact, the tu- 

 bules might well be described as " thin-walled 

 tubular sacs." Evidences of distension by in- 

 ternal pressure are obvious. 



After the larva has been sealed up in its 

 cell by a waxen capping both the fundus of the 

 mid-intestine and the diaphragm-like epithe- 

 liiun closing the cephalic end of the mid-in- 

 testine become perforated, thus establishing an 

 avenue of communication between the mid- and 

 hind-intestine through which the faecal ac- 

 cumulations of the mid-intestine are expelled. 

 At the same time that this occurs each of the 

 Malpighian tubules establishes connection with 

 the hind-intestine by means of a fine canal 

 which perforates the diaphragm-like layer of 

 cells which formerly closed the anterior end 

 of the hind-intestine but which now forms an 

 annular structure uniting the mid- and hind- 

 intestines. Sections through the tubules show 

 that they have greatly diminished in calibre, 

 the walls being more or less collapsed and their 

 component cells being correspondingly nar- 

 rower and deeper. 



The history of the Malpighian tubules and 

 that of the mid-intestine during the feeding 

 period of larval life are therefore parallel in 

 that both, in addition to performing their 



