of a Species of Chironomus. 41 



to and fro with all its ova, the ova separated from one an- 

 other and fell out of the ovary during its preparation, so that 

 only rudiments of the ovary with a few undeveloped ova 

 could be obtained. Notwithstanding this, I have thoroughly 

 investigated the structure both of the entire ovary and of its 

 individual parts. I frequently succeeded in extracting the 

 ovary only partially, obtaining a fragment of the peritoneal 

 envelope of the ovary, and a series of the remains of the 

 ovarian tubes. These consist in the present case of not 

 more than four chambers, reckoning even the least-developed 

 one, representing the so-called vitelline or terminal chamber, 

 according to Glaus*. 



A perfectly developed ovary of our larva (fig. 8) consists of 

 a bundle of ovarian tubes, of which we have counted as many 

 as eight t ; these ovarian tubes consist, as we have frequently 

 observed f , of an extremely elastic structureless membrane, 

 lined internally with a layer of epithelial cells. The contents 

 of these tubes consist of a ductile mass §, in which lie the 

 vitelligenous cells, which usually contain several nucleolar 

 corpuscles, and a larger nucleus with only one nucleolar cor- 

 puscle. By the division of these contents a whole series of 

 compartments or germ-chambers are produced, in each of 

 which is developed an ovum; so that such a many-chambered || 

 ovarian tube may be regarded as an egg-colony : comjaaring 

 it, for example, to a Tapeworm — just as the latter consists of a 

 series of independent individuals, which only cohere during 

 the period of their incomplete development, and are arranged 

 according to their degree of maturity, so also does the ovarian 

 tube (but, of course, not its envelope) consist of a complete 

 series of similarly arranged germ-chambers ; those most highly 



* " Beob. iiber die Bildung des Insecteneies," Zeitschr. fiir wiss. Zool. 

 1864, p. 43. 



t Their number is very different in different insects. Thus Liparis 

 aurijlua has four ovarian tubes (Meyer), and some Coccidae as many as 

 twenty (Leuckart, "Die Fortpflanzimg der Rindenlause," Arch, fiir 

 Naturg. 1857). 



X This is mentioned also by Glaus (in Lecanium, I. e. p. 43), Leydig 

 (I. e. p. 52), and others. 



§ Meyer says it is albuminous {I. c. p. 191). 



II In each ovarian tube of many insects, as also in our Chironomus, 

 several ova are constantly developed ; but in others only one ovum is 

 developed in each, as, for example, in Lecanimn (Glaus) and generally in 

 most Coccidae (Leuckart, "Die Fortpfl. der Rindenliiuse," Arch, fiir Na- 

 turg. 1859, p. 216). Hovrever, no sharp limit exists betv^^een the single- 

 and many-chambered ovarian tubes ; for the ovarian tubes of some in- 

 sects, as, for instance, Cherm.es laricis (Leuckart, /. c. p. 217), may be 

 regarded as at once many- and single-chambered, because here the second 

 germ-chamber is only formed after the complete development of the 

 first. 



