146 NOTES AND MEMORANDA. 



speed to Astraclian, in order there to set about the roicroscopic inves- 

 tigation of the eggs. But when, after four days' travelling, I arrived 

 in a Kussian village, Jandiki, near the shore of the Caspian Sea, and 

 inspected my two bottles, I found in them only a couple of dead, 

 opaque eggs, all the others having entirely disappeared. Fortunately 

 I succeeded in Jandiki, where there is also a small plantation, in 

 obtaining fresh material of the same kind, and this I brought in good 

 condition to Astrachan, making the journey by steamboat. In the 

 town of Astrachan I was able to borrow a Hartnack's Microscope from 

 a medical man practising there, and on a second journey took it with 

 me to Jandiki. In this way I was enabled to make out the chief 

 features of the developmental history of Geophilus by the use of my 

 less seriously affected left eye. At the same time, in spite of the 

 very favourable character of the GeopMlus eggs for microscopic re- 

 search, I could not bring my work to the desired degree of complete- 

 ness." 



Determination and pluck, Professor Lankester adds, have their 

 scope in embryology ! 



Degeneration of the Visual Organs in Arachnida. — Among 

 the group of pseudo-scorpions, some, such as CheUfer, have well- 

 developed eyes, while others, such as Cliernes, are usually said to be 

 quite devoid of visual organs. The interesting discovery has, however, 

 been made by Anton Stecker, of Prague,* that certain individuals of 

 the latter genus possess eyes, although in a rudimentary condition. In 

 specimens of C. cimicoides, Stecker observed on the cephalo-thoracic 

 shield, in the position of the eyes of CheUfer, clear, somewhat trans- 

 parent spots, the chitin forming them being devoid of the granulations 

 covering the rest of the shield. These structures have quite the 

 appearance of corneas, but their visual nature is put beyond queslion 

 by the remarkable fact that each is supplied by a large and well- 

 developed optic nerve, proceeding from an optic ganglion in connec- 

 tion with the brain. The characteristic anthropod end-apparatus — 

 the layer of crystalline rods — was, however, wholly absent. 



About 30 to 35 per cent, of the specimens of Cherries cimicoides 

 examined possessed these eye-spots ; in the remaining 65 to 70 per cent, 

 they are absent, as well as the optic nerves ; while there was only one, or 

 even no, recognizable rudiment of an optic ganglion. It was also made 

 out that the offspring of parents, both of which had eyes, were them- 

 selves provided with these organs ; but that if either the father or 

 the mother were blind, the young were blind too, having, at most, a 

 feeble indication of optic lobes. 



As the author remarks, we have here a most instructive case of the 

 gradual atrophy of an organ by disease, owing to the influence of changed 

 conditions. There can be little doubt that the ancestors of Chernes 

 possessed well-developed eyes ; the disappearance of the crystalline 

 cones and of the characteristic structure of the cornea seems to have 

 been the first step in the retrogressive process, the optic nerve and 

 ganglion remaining in a fairly well-developed state after the true per- 



* ' Morphologisches Jahrbuch,' vol. iv. (1878) p. 279. 



