DACTYLIUS ACULEATUS. 439 



distinguished by the naked eye. On immersing them in spirits of wine they 

 soon became white and opaque. They were of two sizes ; the larger 

 worms being more numerous than the smaller. 



" A slight examination at once convinced me that these worms could not 

 belong to any of the species of entozoa at present known to infest man ; 

 and, considering the period of the year, I was at first induced to imagine 

 that they must be the larva of some insect. On placing one in the field 

 of the microscope, I recognised a beautiful organization, and true nematoid 

 structure ; and, on reference to Rudolphi's ' Synopsis Entozoorum,' and 

 other works on this subject, I discovered that it was an entozoon which 

 had not hitherto been described. Having received several of these worms 

 from Mr. Drake, at different times, I have had an opportunity of making 

 repeated examinations of them by the aid of the microscope, in which 

 I have had the advantage of the kind assistance of Professor Owen and 

 Mr. John Quekett. The animals, being alive and active, formed very 

 interesting objects, as we could readily see and watch the curious actions 

 taking place in their interior. 



" The worm is of a light colour, cylindrical in its form, and annulated, 

 and tapers slightly towards both the extremities, but chiefly towards the 

 anterior, which is the smaller. The female measures about four-fifths of 

 an inch in length ; the male, as is the case with most of the nematoid 

 worms, is much smaller, being about two fifths of an inch long. They 

 vary, however, a good deal in size, especially the males. The head of the 

 worm is obtuse and truncated, and has an orbicular mouth. The mouth 

 is generally not very apparent, and several worms were examined before 

 I succeeded in discovering it. The neck is distinctly annulated. The 

 tail is obtuse and also annulated, but not so much so as the neck. The 

 tegument is a delicate transparent structure, containing two layers of 

 fibres, one circular and the other longitudinal, both of which I believe to 

 be muscular. After the rupture of a worm which had been in dilute 

 spirit, these fibres were seen with great distinctness projecting at the 

 injured part. The tegument is armed with a number of sharp-pointed 

 spines, arranged in clusters of three or four, and sometimes five, in longi- 

 tudinal equi-distant rows. The intervals between the spines in each row, 

 measured by means of the micrometer, were found to vary from one 

 fiftieth to one seventieth of an inch. With the exception of a small part 

 of the body to be noticed presently, the tegument was completely defended 

 by these spines, which were detected as near the head as the third ring, 

 and also close to the extremity of the tail. It was generally observed 

 that, at the anterior part of the body, the spines were directed posteriorly, 

 whilst about the centre they projected outwards, and near the tail pointed 

 towards the head. On examining the worm slightly compressed between 

 two pieces of glass in the field of the microscope, I often obtained a lateral 

 view of the spines attached to the sides of the animal, and I could then 

 very distinctly discern their motions, the animal having apparently the 

 power of protruding and retracting them at pleasure. The spines are 

 attached to the external tegument, into which, when retracted, they are 

 received ; and they appear to be moved by a number of fibres radiating 

 outwards, in the substance of the tegument. The alimentary canal 

 appeared, on some occasions, of a light, vellow colour ; on others, it 

 presented a brownish hue. Upon examining a large female worm, the 

 alimentary canal appeared to commence at the mouth, by three small 



