32 M. Oscar von Grimm on the Agamic Reproduction 



quently to do with a case of asexual reproduction by an im- 

 perfectly developed insect ; that is to say, I had before me an 

 insect which is subject to what Von Baer calls pcedogenesis *. 

 But as I was obliged to interrupt my investigations during 

 the whole summer, I resumed them in the autumn ; and now, 

 as it seems to me that I have attained to sufficiently inter- 

 esting results, I venture to describe my researches, although I 

 can perceive many deficiencies in my investigation. 



I. Pcedogenesis of the species o/" Chironomus observed. 



In the eggs detected by me there were developed larvae 

 0*47 millimetre in length (PI. III. fig, 2), and very similar in 

 their structure to the larvae of Chironomus described by Weis- 

 mann f. They are transparent, clear, and of a yellowish 

 colour, possess a large head, a broad thorax, and a nine-jointed 

 abdomen, the segments of which are pretty sharply separated 

 from each other. The mouth consists of two pairs of very 

 strong brownish jaws {md^ mx), of which the lower pair, having 

 the median margins soldered together, is converted into an 

 immovable lip. The small palpi {_p) attached to the upper 

 lip are chiefly serviceable to the larva in feeding. The an- 

 tennaj (a) are large and composed of six joints, of which the 

 last four form a style, which is surrounded at the base by six 

 setse ; the basal joint bears a large seta, nearly equal in length 

 to the second joint. On the sides of the head the little eyes 

 (e) are situated, with some brownish points near them. The 

 thorax possesses on its venti-al surface a transverse fold, which 

 is divided in the middle by a deep furrow, and transformed 

 into a ])air of clinging-feet i,ff). These are furnished with 

 claws, the number of Avhich afterwards increases. As the deve- 

 lopment of the larva advances the feet become elongated, until 

 finally, after the casting of the third skin, they reach to the 

 mouth (fig. 3,ff). The last abdominal segment also possesses 

 a pair of feet (/{/), which are likewise furnished with claws, but 

 much stronger ones than those on the anterior feet. Besides 

 these Ave find at the same place four finger-like processes (/"), 

 w^hich are seated close to tlie anus, and servo for the respira- 

 tion of the larva J. The upper angle of this same segment is 

 furnished wnth two tufts of very Img hairs. In the interior 



• For K. E. YOU Baer on Prof. \. Wnpior's discovery of larv.TS that 

 propn^'ate, Ganin's similar and siippleniontary observations, and on psedo- 

 genesis in general, see Mel. Hiol. de TAend. de St. Petei"sb. tome v. 



t Dr. A. Weismann, " Die Kntwickluug der Dipteren im Ei, nach Beo- 

 bachtnngen an Chirononius ?\^.':', Musca vowitoria und Piih'.i- Canh<," 

 Zeitschr. fiir wiss. Zool. xiii. p. 148. 



\ Weismann, /. r. p. 148. 



